tailors the times passed to stockfish

gives a buffer for low time (makes them think they have less time than they have
to avoid timing out due to lag) and limits the time to 30s to stop them from ever
thinking too deeply.
changes User._register to create a new set of details

there was a bug where the username was still Anonymous because of the
change to allow registering while in games/logged in.

only the prefs and the last seek are carried over from the current
user now; everything else is reset when you register (including rating
and recently completed rated games)