Removed _change_notify

-For inspector refresh, the inspector now detects if a property change by polling a few times per second and then does update the control if so. This process is very cheap.
-For property list refresh, a new signal (property_list_changed) was added to Object. _change_notify() is replaced by notify_property_list_changed()
-Changed all objects using the old method to the signal, or just deleted the calls to _change_notify(<property>) since they are unnecesary now.

scene/2d/polygon_2d.cpp

@@ -483,7 +483,6 @@ void Polygon2D::set_offset(const Vector2 &p_offset) {
 	offset = p_offset;
 	rect_cache_dirty = true;
 	update();
-	_change_notify("offset");
 }
 
 Vector2 Polygon2D::get_offset() const {