Fixed Postgresql Notes search issue (integer vs string) v2.
Created by: jozefvaclavik
I created app/roles/noteable.rb where I implemented necessary changes. This file is included in app/model/issue.rb, app/model/snippet.rb, app/model/wiki.rb, and in app/model/merge_request.rb where I also changed mr_and_commit_notes. I hope everything is Ok now.
Improved #2234 Fixes #1957