controllers: move controllers base class from lib/base to controllers

TG quickstart put it in lib/base.py , but it fits better on the controllers
layer as a base there.

The contributing docs were a bit ahead of time ... but with a typo.

py3: use inspect.getfullargspec instead of deprecated inspect.getargspec

Avoid some pytest warnings.

py3: trivial renaming of .iteritems() to .items()

A bit like "2to3 -f dict", but we don't want list().

lib: clean up ext_json and how it is used - avoid monkey patching

Note that py3 json.dumps will return ASCII (with all unicode escaped) encoded
as str. But we generally want JSON as bytes (which json.loads also can read),
so also wrap the result with ascii_bytes in many places.

lib: refactor _get_access_path as get_path_info

We will need it later when it gets more tricky to get the path from environ ...

py3: only use safe_str for string conversion - not for arbitrary __str__ invocation

Usually, we actually just want unicode string, and it is better to just unicode().

py3: cleanup map usage and avoid py3 ambiguity

Based on 2to3 -f map ... but replace map with something more explicit (unless
born and raised in a lisp world) (but sometimes slightly more verbose).

py3: prepare for types.NotImplementedType going away

From 2to3 types.

auth: consistently use request.authuser - drop request.user

This seems like old tech debt. Now, just get rid of it.

backend: replace Pylons with TurboGears2

Replace the no-longer-supported Pylons application framework by TurboGears2
which is largely compatible/similar to Pylons.
Some interesting history is described at:
https://en.wikipedia.org/wiki/TurboGears

Changes by Dominik Ruf:
- fix sql config in test.ini

Changes by Thomas De Schampheleire:
- set-up of test suite
- tests: 'fix' repo archival test failure
Between Pylons and TurboGears2, there seems to be a small difference in the
headers sent for repository archive files, related to character encoding.
It is assumed that this difference is not important, and that the test
should just align with reality.
- remove need to import helpers/app_globals in lib
TurboGears2 by default expects helpers and app_globals to be available
in lib. For this reason kallithea/lib/__init__.py was originally changed
to include those files. However, this triggered several types of
circular import problems. If module A imported something from lib (e.g.
lib.annotate), and lib.helpers imported (possibly indirectly) module A,
then there was a circular import. Fix this by overruling the relevant
method of tg AppConfig, which is also hinted in the TurboGears2 code.
Hereby, the include of something from lib does not automatically import
helpers, greatly reducing the chances of circular import problems.
- make sure HTTP error '400' uses the custom error pages
TurboGears2 does not by default handle HTTP status code
'400 (Bad Request)' via the custom error page handling, causing a
standard non-styled error page.
- disable transaction manager
Kallithea currently handles its own transactions and does not need the
TurboGears2 transaction manager. However, TurboGears2 tries to enable it
by default and fails, throwing an error during application initialization.
The error itself seemed to be harmless for normal application functioning,
but was nevertheless confusing.
- add backlash as required dependency: backlash is meant as the WebError
replacement in TurboGears2 (originally WebError is part of Pylons). When
debug==true, it provides an interactive debugger in the browser. When
debug==false, backlash is necessary to show backtraces on the console.
- misc fixes

tg: minimize future diff by some mocking and replacing some pylons imports with tg

No actual tg dependency yet, just a temporary hack faking tg as an alias for
pylons.

Based on work by Alessandro Molina.

controllers: avoid setting request state in controller instances - set it in the thread global request variable

In TurboGears, controllers are singletons and we should avoid using instance
variables for any volatile data. Instead, use the "global thread local" request
context.

With everything in request, some use of c is dropped.

Note: kallithea/controllers/api/__init__.py still use instance variables that
will cause problems with TurboGears.

api: fail when given unknown arguments

This make the API more type safe and can help developers fix issues early.

api: set authuser in the thread global request instace - and temporarily verify that it matches what is passed explicitly to auth methods

This makes it more like what middleware / controllers do for "normal" HTTP requests.

compat: drop unnecessary wrappers for old Python versions

Made unnecessary by other cleanup or upgrade to Python 2.6+.

api: avoid sending double Content-Length header (Issue #201)

WSGI will take of Content-Length - handling it explicitly was misguided.

cleanup: consistently use 'except ... as ...:'

Use the Python 2.6+ syntax instead of the old confusing 'except ..., ...'
syntax.

auth: construct AuthUser from either user_id or db.User object

If the caller already has the database User object, there's no reason
for AuthUser to look it up again.

The `api_key` lookup functionality is dropped, because 1) it's only
used in one place, and 2) it's simple enough for the caller to do the
lookup itself.

The `user_id` lookup functionality is kept, because 1) it's frequently
used, and 2) far from a simple `User.get(id)` lookup, it has a complex
interaction with UserModel. (That cleanup will have to wait for another
day.)

All calls of the form `AuthUser(user_id=x.user_id)` can be replaced with
`AuthUser(dbuser=x)`, assuming `x` is a db.User. However, verifying that
assumption requires a manual audit of every call site, since `x` might
also be another `AuthUser` object, for instance. Therefore, only the
most obvious call sites have been fixed here.

auth: remove redundant AuthUser constructor arguments

AuthUser looks up the user based on the first of `user_id`, `api_key`
and `username` that is not None *and* does not refer to the default
(anonymous) user. In practice, the arguments always refer to the same
user, so there's no point in specifying more than one of them.

AuthUser: simplify check_ip_allowed and drop is_ip_allowed

check_ip_allowed is always called with user_id and inherit_from_default
arguments taken from the same User/AuthUser object, so just take that
object instead. This simplifies the is_ip_allowed method to the point
where it can be removed.

AuthUser: Drop ip_addr field

None of the AuthUser consumers actually need to get the IP address from
the AuthUser object, so it's just redundant.

Also, AuthUser represents a user session, and should not be used as a
generic user + IP address data structure.

Correct licensing information in individual files.

The top-level license file is now LICENSE.md.

Also, in various places where there should have been joint copyright holders
listed, a single copyright holder was listed. It does not appear easy to add
a link to a large list of copyright holders in these places, so it simply
refers to the fact that various authors hold copyright.

In future, if an easy method is discovered to link to a list from those
places, we should do so.

Finally, text is added to LICENSE.md to point to where the full list of
copyright holders is, and that Kallithea as a whole is GPLv3'd.

Second step in two-part process to rename directories.
This is the actual directory rename.