Drop the git_branch_name from the model and logic

This commit removes `git_branch_name` in the model, the internal API,
the controller, the templates and the forms
Remove all mention of `git_branch_name` from the unit-tests
Remove mentions of the clt_gitbranch which is used for git_branch_name
Bring back the collection.branchname in the query
Use the old gitbranchname as new branch_name except if there was no gitbranchname
Change the branchname from F-* to f*

This is made so that the unit-tests are consistent with the branchname
used in production. With the drop of gitbranchname in favor of branchanme
the branch format for Fedora changed from F-* to f*, just like the git
branch actually used.
The `master` branch is now known as the `devel` branch, adjust the tests accordingly