Update usergroups.xml version code
Drop `useragent` column before upgrading
Update Standards
Add ability to rebuild/reload all caches

MyBB provides the ability to rebuild a single cache, one at a time. It is often desirable to rebuild all caches (for example, when you switch to a new cache handler).
Update Standards
Update version check task
Revert "Double-escaping the user's data and enhanced the website verification enhancement."

This was reverted in the stable branch but needs to be reverted in the feature branch too. Other avenues will be explored to improve these areas.
Remove `text-decoration: underline` from ACP links

These look woefully out of place on the new theme.