Make detecting bare Git repositories more robust

Git remote repositories may end on '.git', e.g. myrepo.git. Just checking
for a repository path to end on '.git' causes 'Repository not found' errors
in such a case. To distinguish between bare and normal Git repositories,
check if there is a '/.git' part at the end of the repository path
(i.e. if GIT_DIR is pointing to '.' (bare) or '.git').

#518 multiple issues patterns
- added logging
- some code cleanup
- added example of wiki pattern to .ini file
- updated contributors and changelog

Allowing multiple issue servers to be autolinked in the changeset view;
linking is now contingent on issue_server_link, issue_pat and issue_prefix
being defined; multiple servers can be used by specifying a common suffix on all
the above variables, ie ..

issue_server_link_1
issue_pat_1
issue_prefix_1

.. and ..

issue_server_link_other
issue_pat_other
issue_prefix_other

.. would be treated as two distinct servers, but ..

issue_pat_thing

.. would be ignored (since the other two requisite vars aren't present).

This patch is backwards compatible with existing variables (as a suffix
isn't needed).

fixed #570 explicit users group permissions can overwrite owner permissions
- added test for that case

swap the select values with revisions dynamically when switching the repos on pull request view
- fix the partial ajax request that should never do redirect

fixes #567 diff non-unicode encoding missmatch
- now uses safe_unicode ass all other parts of the system

fixes issues #566 non-ascii search params are crashing paginator
- those arguments needs to be converted to strings

Implemented patch from andrewsh ref #565 Add support for {netloc} and {scheme}
to alternative_gravatar_url

Implemented permissions for writing to repo
groups. Now only write access to group allows to create a repostiory
within that group

fixed issue #559 fixed bug in routing that mapped repo names with <name>_<num> in name as
if it was a request to url by repository ID

Permissions on group can be set in recursive mode setting defined permission to all children
- more explicit permissions
- fixes for empty values in permission form

Fixing issues of cache invalidation for multiple instances running in rhodecode.
- during server start always register all cache keys for all repositories
- Don't clear cache markers on start since multiple instances can clear each other out

Fixed status of changesets in preview windows
- show what status was pull-requests closed with
- added alternative logic for showing that status (disabled for now)

fixes #550 mercurial repositories comparision failed when origin repo had
additional not-common changesets + added regresion test for this

Remove null from revision column as for comments inside pull requests to work properly
new migration adds column for future simpler main page

Added huge diff protection for RSS/ATOM feeds.
It can really be a performance killer for huge diffs.