[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.cpp

@@ -81,7 +81,7 @@ void NPCManager::updateNPCPosition(int32_t id, int X, int Y, int Z, uint64_t I,
     Chunking::updateEntityChunk({id}, oldChunk, newChunk);
 }
 
-void NPCManager::sendToViewable(BaseNPC *npc, void *buf, uint32_t type, size_t size) {
+void NPCManager::sendToViewable(Entity *npc, void *buf, uint32_t type, size_t size) {
     for (auto it = npc->viewableChunks.begin(); it != npc->viewableChunks.end(); it++) {
         Chunk* chunk = *it;
         for (const EntityRef& ref : chunk->entities) {