Create an "add" button to add a Form to a list of Forms
This uses the toolbar infrastructure.
In the first patch the button doesn't do anything.
Note: It might not be possible to split this from the next task that wires the add button.
Make sure the browser test succeeds at this step.

Make the "add" button display the "add Form" form
This patch creates the wiring to the Form widget previously created.
Add Form to List of Forms and put Form to edit mode.