API client class v1.1.62

• 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