Fix link, there is no need to specify the collection
Restrict the list of available collections to 'master' unless the user is an admin
Admins are allowed to retire a package on multiple branches
Rework a bit the bugzilla api logic

- Rely on integer comparison to get the branches with the highest version
  (cheat and put devel at 10,000 unless that branch is orphaned)
- If the don't have an owner and the current branch is not orphaned, no
  matter the version, take that point of contact
- Add a little documentation about the values returned by the SQL query
Replace the branchname ``devel`` by ``master`` to fit what is in production
Update API documentation s/devel/master/