• added methods/functions to manage AP groups: list_apgroups(), create_apgroup(), edit_apgroup(), and delete_apgroup() (only supported with controller versions 6.0.X and higher)
• adapted code to handle the behavior of the new v2 API routes that were added with controller versions 6.0.X and higher
• merged PR #76 which adds methods/functions check_controller_update() and check_firmware_update(), contributed by @brenard
• further work on updating method/function comments to PHPDoc format (PSR-5)