Add requests-tests-repo command
    
    This patch adds a command for adding new repository in the tests
    namespace. The only required parameter is the module name and the
    description of the repository.
    
    An example of issue filed by the new command:
    
       https://stg.pagure.io/releng/fedora-scm-requests/issue/47
    
    Resolves:
    
       https://pagure.io/fedpkg/issue/176
    
    Signed-off-by: Miroslav Vadkerti <mvadkert@redhat.com>