Fixed Postgresql Notes search issue (integer vs string)

Created by: jozefvaclavik

Hi,

I override notes methods for classes that use has_many :notes, as: :noteable Method is manually converting id to string to avoid type crash for postgresql database. I also had to update mr_and_commit_notes method. I tested issues and snippets it in production. I somehow cant find where to write wiki note, but it should work as well. And because I don't have any merge requests, i couldn't test changed method either. If anything, let me know. Fixes #1957

Jozef