Before we have only owner_id to determine group owner
With multiple owners per group we should get rid of owner_id in group.
So from now @group.owner will always be nil but
@group.owners return an actual array of users who can admin this group

* Hooks and team pages allowed only for masters/owners
* Group page allowed for admin
* Corrent authentication for Projects controller
* Hide some project elements from visitor

* Render right layout depends on current_user
* show sample git username/email when repo is empty
* Show extra info when browsing public area
* Fixed some tests related to public projects
* show comments in read-only for public projects
* Remove old public routing

GITLAB-1279 (GITLAB-1264)

Change-Id: Ifb5b4313bc91fae720f8ef5c36152c45e9d38934

* Show new merge request button from compare page
* Show message if user selected same branches
* Show message if compared branches are the same
* Prepend inputs with from/to labels

Placeholder in search field was wrong

When viewing the diff for a changed image file, two bugs occur:

- Both the 'before' and 'after' images link to the 'after' commit
- Visiting the link for either image will cause a error

The first is caused by both image links referencing '@commit.id' rather
than '@commit.parent_id'.  The second is caused by the use of
'project_tree_path' which is used for creating links to directories in
the git file tree. 'project_blob_path' which links to files should be
used instead.