Organize Entity header

Probably the third or fourth pass of this darn header...  Just keep making it better every time
Rename some functions to make more sense to a reader
Use different method for Observing/subscribing to component events
Get rid of abomination of overloading GetParentUser

dGame/dGameMessages/GameMessageHandler.cpp

@@ -143,7 +143,7 @@ void GameMessageHandler::HandleMessage(RakNet::BitStream* inStream, const System
 		}
 
 		//Kill player if health == 0
-		if (entity->GetIsDead()) {
+		if (entity->IsDead()) {
 			entity->Smash(entity->GetObjectID());
 		}