Remove unnecessary recalculatePermissibles call

Closes #1580
First attempt at improving interaction with LilyPad

Closes #1557
Fix FieldReplacer to correctly replace fields in superclasses
Perform backups of permissions backend before each schema upgrade

Correct MySQL database encoding to accept unicode characters outside of
the BMP

Fixes #1552
Include number of users in a group when listing users

Fixes #1606
Include data for any backend in error report

Previously only data for file backend was included.

Fixes #1559