Make things less debug-y, introduce the start of scripted waves, UX improvements

src/main/java/gg/malloc/defense/model/Game.java

@@ -1,6 +1,8 @@
 package gg.malloc.defense.model;
+import org.bukkit.entity.Entity;
 
 public interface Game {
   int getWaveCount();
   Wave getWave(int waveNumber);
+  default void onMobDamaged(Entity entity) {}
 }

src/main/java/gg/malloc/defense/model/Wave.java

@@ -2,6 +2,5 @@ package gg.malloc.defense.model;
 
 public interface Wave {
   int batchCount();
-  int totalMobCount();
   void spawnBatch(Spawner spawner, int batch);
 }