New - custom lorax templates for livemedia tasks
    
    This adds two new options (--lorax_url and --lorax_dir) to the Koji CLI
    so that it's now possible to use custom lorax templates for livemedia
    tasks.  The custom templates must come from a supported, allowed SCM,
    which makes it trivial to inject the whole directory structure of
    template files that lorax expects.
    
    In addition to the CLI changes, kojid's LiveMediaTask handler recognizes
    these new options and acts accordingly by extending the
    livemedia-creator call via its --lorax-templates option.