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.

auth: restore anonymous repository access

Dominik Ruf found that aa25ef34ebab introduced a regression in anonymous access
to repositories ... if that is enabled.

The refactoring was too strict when it missed that not all repo permission
checks require a logged in user. Read access can be granted to the default user
... but not write or admin.

Instead of the commands used in aa25ef34ebab, the following commands are used
to consistently also allow the default user in all decorators where we only need
repo read access:

# Introduce explicit allow_default_user=True - that was the default before aa25ef34ebab
sed -i 's/@LoginRequired()/@LoginRequired(allow_default_user=True)/g' `hg mani`
sed -i 's/@LoginRequired(\(..*\))/@LoginRequired(\1, allow_default_user=True)/g' `hg mani`
# The primary case: Replace @NotAnonymous with removal of allow_default_user=True
perl -0pi -e 's/\@LoginRequired\((?:(.*), )?allow_default_user=True\)\n\s*\@NotAnonymous\(\)/\@LoginRequired(\1)/g' `hg mani`
# If there is a global permission check, no anonymous is ever allowed
perl -0pi -e 's/\@LoginRequired\(allow_default_user=True\)(\n\s*\@HasPermission)/\@LoginRequired()\1/g' `hg mani`
# Repo access for write or admin also assume no default user
perl -0pi -e 's/\@LoginRequired\(allow_default_user=True\)(\n\s*\@HasRepoPermissionLevelDecorator\('"'(write|admin)'"'\))/\@LoginRequired()\1/g' `hg mani`

controllers: remove empty __before__ methods

__before__ methods that only call the super __before__ method are redundant
and can be removed. The super's method will be called directly.

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.

auth: simplify repository permission checks

In practice, Kallithea has the 'repository.admin' permission imply the
'repository.write' permission, which again implies 'repository.read'.

This codifies/enforces this practice by replacing HasRepoPermissionAny
"perm function" with the new HasRepositoryLevel function, reducing the
risk of errors and saving quite a lot of typing.

helpers: move Page/RepoPage to a separate file page.py

The Page and RepoPage classes are not used from templates and thus do not
belong in helpers.
They could have been put in utils.py, but because they are completely
standalone we can easily split them to a separate file.

controllers: simplify request.GET.get for safe_int

Don't specify the default value twice - the one for safe_int is enough.

controllers: don't pass rendered templates in context variables

Some controllers used the followifng pattern:
- render a data template into a context variable
- for partial (ajax) requests, return the contents of this variable
- for full-page requests, render the full page, which expands the value of
the context variable

Instead, avoid context variables let the controller simply render the full or partial page, and let
the full page template include the partial page.

Remove this context variable for templating and use render exclusively.
From templates, use %include instead of context variables.

This in line with the suggestions in the Pylons documentation:
http://pylons-webframework.readthedocs.org/en/latest/helpers.html#partial-updates-with-ajax

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.