[api] fix decline of add_role, set_bugowner and delete requests when permissions are just defined in package, but not project (bnc#833616).
[api] renaming the routes for deleting user roles
[webui] more RESTfull approach when adding and removing relationships
[api] Thinking Sphinx based search

 * It requires indexing (rake ts:rebuild) once in a while in order to work.
 * Migration included (just a new db index) to speedup indexing
[api] Thinking Sphinx related files added to .gitignore
[webui] Use the new sphinx-based search

 * The new search resource is used for projects and packages, not for owners.
 * Results change slightly because the new searching does not search in
   substrings, only full words.
 * kaminari included for pagination.
[api] move maintainer/owner handling into own modul
[webui][api] Introduce comments for projects, package and requests in the API and display them in the UI
[api] fix testing