Use existing methods for branch names: Ex use @repository.branch_names instead of @repository.heads.map(&:name)

I discovered while trying to use UserTeam#remove_member() that
UsersProject.in_projects was broken.  So I wrote test cases to test what
I was trying to do and fixed the underlying problem.

It uses params[:id] instead of request.fullpath.
It should fix #3132.

Most of these are comments but a few are strings for users.

Might be an idea to run this from time to time:
https://github.com/lyda/misspell-check

It runs mostly clean now.