Added functionality to handle NPC storage and retrieval.
Created NPC class and moved shared functionality here from Player.
Removed shared information with NPC, extended NPC.  Added check to look() method to list NPCs currently in the room.
Added static constants for name min length and max length.
Added static constants for name min length and max length.
Added getWordsUpToIndex() method.
Added commands to create, delete, and modify NPCs.