User Mentions Improvements by Xon 2.9.0

• Require XF2.1+, remove XF2.0 support
• Fix matching usergroups had lower priority than matching users in backend, where the frontend and XF1 version the user-group had priority

• Do not constantly append ?c=... to user group avatar URL when editing the a user group

• Implement "Send quote emails only on unreplied threads" option which was missed
  

• Support Push notifications with usergroup mentions (changes several add-on phrases & templates)
• Compatibility fix for Report Centre Essentials v2.2.0+
• Fix linking to usergroup mentions in alerts

• Fix mention/quotes email being sent if a user's account state is invalid, or the triggering user is ignored

• php 7.4 compatibility update (Requires XF v2.1.3)

• Add options icon
• Only display "receive email when mentioned/quoted" preference options if the feature is enabled for users

• Fix minor php 7.3+ compatibility issue (optional admin triggered task to rebuild permissions)

• Extend user's Account Privacy saving process to also save email options

• XF2.1.1 compatibility bugfix