[WIP] Convert most of Chunking to Entity-based system

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.

src/Eggs.hpp

@@ -1,19 +1,7 @@
 #pragma once
 
 #include "core/Core.hpp"
-#include "NPC.hpp"
-
-struct Egg : public BaseNPC {
-    bool summoned;
-    bool dead = false;
-    time_t deadUntil;
-
-    Egg(int x, int y, int z, uint64_t iID, int type, int32_t id, bool summon)
-        : BaseNPC(x, y, z, 0, iID, type, id) {
-        summoned = summon;
-        npcClass = NPCClass::NPC_EGG;
-    }
-};
+#include "Entities.hpp"
 
 struct EggType {
     int dropCrateId;