[refactor] New buff framework (player implementation)

Get rid of `iConditionBitFlag` in favor of a system of individual buff
objects that get composited to a bitflag on-the-fly.
Buff objects can have callbacks for application, expiration, and tick,
making them pretty flexible. Scripting languages can eventually use
these for custom behavior, too.

TODO:
- Get rid of bitflag in BaseNPC
- Apply buffs from passive nano powers
- Apply buffs from active nano powers
- Move eggs to new system
- ???

src/NPCManager.hpp

@@ -42,7 +42,7 @@ namespace NPCManager {
     void destroyNPC(int32_t);
     void updateNPCPosition(int32_t, int X, int Y, int Z, uint64_t I, int angle);
 
-    void sendToViewable(BaseNPC* npc, void* buf, uint32_t type, size_t size);
+    void sendToViewable(Entity* npc, void* buf, uint32_t type, size_t size);
 
     BaseNPC *summonNPC(int x, int y, int z, uint64_t instance, int type, bool respawn=false, bool baseInstance=false);