Improvements to time handling:
 - Long ticks are now broken up into subticks for component system processing
 - Really long ticks are capped
 - Game time now reflects the sum of deltas.
 - World time is now in ms of relative time, so a day in world time is the same number of ms as a realtime day.
 - Various interface cleanup.
Game time is now persisted
Bit of refactoring of the save game format in preparation for multiple world support.
Removed some old classes that were unused.
A couple of small fixes to chunk generator.