Player and all NPCs now have a common superclass, with virtual functions
so smooth over shared behavior. EntityRef is a simple class that points
to an arbitrary Entity.
This commit is not yet functional.
We had avoided putting STL containers into Players back when we thought
Players was still POD and needed to remain POD, but it turned out that
neither were the case all along, so there's no need for the indirection.
ChatManager -> Chat
MissionManager -> Missions
NanoManager -> Nanos
TransportManager -> Transport
ChunkManager -> Chunking
BuddyManager -> Buddies
GroupManager -> Groups
RacingManager -> Racing
ItemManager -> Items
NPCManager and PlayerManager remain.
Note: You can use git log --follow src/file.cpp to trace the history of
a file from before it was renamed.
