- added several monthly stats methods: `stat_monthly_gateway()`, `stat_monthly_site()`, `stat_monthly_aps()`, `stat_monthly_user()`, thanks go to Roel Janssens for spotting these MongoDB collections
- test for `object` or `resource` in `get_curl_resource()`, closes PR 82 submitted by banakito
- applied changes to comments in `example/modify_smartpower_pdu_outlet.php` based on a suggestion by thesohoguy
- removed unnecessary variable from `list_apgroups()`, thanks to Stephen Davies for reporting
- added an optional parameter $ap_group_ids to the `create_wlan()` function/method for UniFi controller versions 6.0.X and higher, thanks to Stephen Davies for contributing