Allow access to groups with public projects.

Fixed Group avatars to only display when user has read
permissions to at least one project in the group.
 Merge branch 'feature/public_groups' into 'master'

Public Groups

This is the initial work (meaning no tests) for making groups public if they have a public project (or internal for logged in users). This allows issues and merge requests to be viewed, but _not_ group membership. As part of this I have also added back the link in the public project title section (it was removed as it didn't make sense before).

This addesses the following suggestions/issues:

http://feedback.gitlab.com/forums/176466-general/suggestions/5314461-groups-containing-one-or-more-public-projects-shou
Issue #32
https://github.com/gitlabhq/gitlabhq/issues/5203
as well as a few closed issues.

This also changes the public user page to only show groups that are accessible to the user in some manner.
Add public groups to change log
Fix commit image js

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Fix onion image control

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>