-begun implementing drag & drop editor wide

-filesystem dock dnd support
-property list dnd support
-scene tree dnd support

tools/editor/plugins/canvas_item_editor_plugin.cpp

@@ -572,6 +572,8 @@ bool CanvasItemEditor::_select(CanvasItem *item, Point2 p_click_pos, bool p_appe
 		_append_canvas_item(item);
 		viewport->update();
 
+		return true;
+
 	} else {
 		//regular selection