added quad primitive, shortcuts and safe entity deletion

editor/include/panels/scene_hierarchy.hpp

@@ -27,6 +27,7 @@ namespace OpenEngine {
 
             Entity GetSelectedEntity() const { return selected_context; };
             void SetSelectedEntity(Entity entity) { selected_context = entity; };
+            void ClearSelection() { selected_context = {}; };
 
         private:
             void DrawEntityNode(Entity& entity);