Unifi-python-api

- allow filtering by multiple MAC addresses in list_devices(), contributed by sgrodzicki, 189

- hotfix to address cookie issues in UniFi OS 3.2.7, reported by tflatebo
- fixed minor typos
- minor code reformatting of the examples
- starting with this release, cookies are no longer supported when connecting to a UniFi OS-based controller
- added set_vlan_to_port.php example, contributed by SamuelSchnelly, 203
- allow additional parameters in `create_wlan()`'s payload, contributed by sgrodzicki, 191

- added generate_backup_site() method, contributed by labo-jad
- added stat/device-basic endpoint 188, contributed by sgrodzicki

- updated README to reflect support for 7.X
- `get_last_error_message()` now always returns a string which is empty if no message is available
- applied PR 151 in slightly different way for consistency with other similar code sections, contributed by banakito
- changed default argument values in several methods/functions from null to an empty string

- fixed `create_radius_account()` method to make Tunnel Type and Medium optional parameters, reported by CodeByJacob

- removed unnecessary CURLOPT_HEADER from the login() method
- added several more possible attributes for client stats
- cast VLAN id to string in create_radius_account()