-getComponent functions for Template and Entity

-error information about adding system with non existing component (prints name of system and component)
-fill components in template with default values

source/ecs/entity.d

@@ -16,10 +16,22 @@ struct Entity
     {
         EntityManager.instance.id_manager.update(this);
     }
+
+    T* getComponent(T)()
+    {
+        EntityManager.EntitiesBlock* block = gEM.getMetaData(&this);
+        EntityManager.EntityInfo* info = block.type_data;
+        return cast(T*)(cast(void*)&this + info.deltas[T.component_id]);
+    }
 }
 
 struct EntityTemplate
 {
     ubyte[] entity_data;
     EntityManager.EntityInfo* info;
+
+    T* getComponent(T)()
+    {
+        return cast(T*)(entity_data.ptr + info.deltas[T.component_id]);
+    }
 }