Expose widget id via widget drop

This is needed in the Row and Column widgets in order to take a user back to the
row or column widget when saving an internal widget.
Merge branch 'master' into row-column-improvements-73002308
Use attr_accessor for widget
Expose a parent widget id if it exists
Run specs
Merge pull request #374 from G5/row-column-improvements-73002308

Row column improvements 73002308