Move form to a partial

[bgates]

Instead of having the form exist in the new and edit (and now index!) templates, put it in a partial and refer to that partial in the new and edit templates.

For the index template, remove the form entirely and bring back the link to Add New Restaurant - but have the link work by xhr to insert the form after the link.

When the new restaurant form is submitted, have it insert the new restaurant row via xhr (which it should be doing now), and then remove the form from the page.