Don't activate/deactivate/remove entities when not needed

core/src/com/me/common/ecs/Entity.java

@@ -39,20 +39,26 @@ public final class Entity {
     }
 
     public void activate() {
+        if (!active) {
             active = true;
             refresh();
         }
+    }
 
     public void deactivate() {
+        if (active) {
             active = false;
             refresh();
         }
+    }
 
     public void remove() {
+        if (!removed) {
             removed = true;
             active = false;
             refresh();
         }
+    }
 
     public Engine getEngine() {
         return this.engine;