Switching over from AdvancedEntityManager to GameEventManager

Most of the logic for which entities were displayed and such resided in
AdvancedEntityManager, however now most of it will be in GameEvents
which are managed by the GameEventManager in much the same way entities
were under AdvancedEntityManager.
Continuing to switch over. Certain events are unprocessed still

Fixed large bug in Add method of LayeredLinkedList. Should be bug-free
now...
Continuing to debug
Continued Debugging

Added LayeredLinkedList.ElementsBetweenBackwards
Added a test of LookupLinkedListSet
Changed GameEvent to a class
Added a Contains method to EntityManager
Many changes to GameEventManager for debugging purposes
Switched the invisibility thing to use an event
Shift slows down the rate at which the time rate changes
Fixed obvious bug in ElementsBetweenBackwards

also added debug prints to make invisible and rewind make invisible
More debugging - FOUND BUG!!!!!!

Error was in LookupLinkedListSet

refnode.Value should have been refnode, forgot to change when
eliminating Reference
Removed debug statements

Only (obvious) bug left is the weird rings that appear every second