Add or remove tags to datasets

def marvcli_tag(ctx, add, remove, datasets):
    """Add or remove tags to datasets"""
    if not any([add, remove]) or not datasets:
        click.echo(ctx.get_help())
        ctx.exit(1)

    app = create_app()
    setids = parse_setids(datasets)
    app.site.tag(setids, add, remove)