Limit spawn amount if too many entities are in the world

Can be controlled in the config with `sceneEntityLimit`

src/main/resources/languages/en-US.json

@@ -306,6 +306,7 @@
     "spawn": {
       "usage": "Usage: spawn <entityID> [amount] [level(monster only)]",
       "success": "Spawned %s of %s.",
+      "limit_reached": "Scene spawn limit reached. Spawning %s entities instead.",
       "description": "Spawns an entity near you"
     },
     "stop": {