The only supported DB at this time is MySQL/MariaDB

A mouse-over now pops up per user when moving the mouse
over them. Migrated the code to use the config helpers
so we don't meddle with $limits ourselves.

We now queue TC changes as changesets so we minimize
the number of events generated. Also make use of
configuration helpers so we don't meddle with the $limits
hash directly.

This replaces the need to directly access $limits