* Defer load of groups data
* Introduce newFromRow()/loadFromRow() to allow bulk loading of user objects from a result set
* Hook email and email authentication save/load to allow CentralAuth to provide a global email address
* Defer save of user data after confirmEmail() and invalidateEmail(). Caller must now also call saveSettings(). This reduces the master query count in some code paths.
Elsewhere:
* Introduce UserArray class, for bulk loading of user objects. Immediately useful in email notification, potentially useful for proposed user alias feature.
* In Special:Confirmemail, remove useless handling for impossible false return from confirmEmail()/invalidateEmail().
