Include regular contributors when checking if user is watching a project
    
    We were checking if the user had set a specific 'watch' flag, if they
    were the creator of the project or part of a group of contributor but
    we forgot to check if the user was a regular contributor who got commit
    to the project.
    
    This fixes it, with unit-tests.
    
    Fixes https://pagure.io/pagure/issue/1601