Username auto-complete using XFES 1.7.1

• Fix XF2.1 support

• Require StandardLib v1.22.0+
• Require Search Improvements v1.17.0+
• Restore XF2.1 support as Search Improvements actually supports XF2.1
• Add Username auto-complete search field boosts option, controls various tunables about search field priorities
• Better selection of exact text and prefix matches not being the top results

• Fix possible internal server error when a guest attempts to logout

• Support for upcoming (paid) "Multiple Account Emails" addon
• Fix a user wasn't re-indexed if the user moved out the mention blocked group
• Fix users 'freshness' was not reliably pushed into the search index, which resulted in the Front-end recent activity cutoff not working as expected
  • Recommend User Essentials v4.5.6+ for best compatibility

• Require StandardLib v1.21.0+
• Require Search Improvements v2.15.4+
• XF2.3 support, requires XF2.3.3+

• Require StandardLib v1.19.0+
• Require Search Improvements 2.12.0+
• Fix admincp quick search could potentially return the same user multiple times

• Fix moving a user in/out of a group which blocks mentions didn't force visibility for mentions to be updated
• Fix indexing queue for pushing user last activity into the search index could skip users
• Workaround edge case where a user's with very old last activity record could be updated but was not pushed into the search index

• Fix duplicate exponential decay being added for username autocomplete (did not appear to affect results)
  If using Search Improvements v2.11.0+, Username autocomplete now prefers prefix matches
  • Recommend updating Search Improvements to v2.11.0+

• Require Standard Library by Xon v1.18.0+
• Add "Block mentions for members of group(s)" option.
  • Removed from front-end user auto-complete
  • Prevents mentioning from sending mention/quote alerts