Unifi-python-api

re-added the upgrade_device() function/method

added start_rolling_upgrade() and cancel_rolling_upgrade() methods/functions

added invite_admin() and revoke_admin() functions/methods

General code cleanup (replace tabs by spaces, etc.)
Methods/functions added:
- list_country_codes()
- set_guestlogin_settings_base()
- set_site_connectivity()
- set_site_country()
- set_site_guest_access()
- set_site_locale()
- set_site_mgmt()
- set_site_name()
- set_site_ntp()
- set_site_snmp()
Examples added:
- ap_upgrade_firmware.php
- site_provisioning_example
- update_ac-iw_ports.php

merged in PR 7
added examples:
- create site
- delete site
- modify WLAN settings for controller version 5.5.X and higher using the `set_device_settings_base()` method, also demonstrates the use of `get_last_results_raw()`

- minor code cleanup and input validation/sanitization improvements
- added delete_device() function/method
- added move_device() function/method
- added optional `type` parameter to stat_sessions()
- updated README