Unify user, group, watches and notification management / storage in FECRU

for historical reasons, user data is stored in two places in FE/CRU:

• infinityDB stores username, email, various prefs
• crucdb stores username, id, email, and various prefs

UPDATE users are now stored in crucdb, however groups, watches, etc are still stored in infdb0. This needs to move across as well so infdb0 can be decommissioned.

this legacy is leading to death by a thousand cuts in support and maintenance.

Unify user data into the crudb.

• migrate data from infinitydb to crudb and decommission infinity DB0
• unify UserManager and CrucibleUserManager: separate security/auth questions into new SecurityManager and move all other user management into a single manager class.

see also FE-2707