Forms - fill out mode #47

Now that we can (for the most part) create forms in the editor, we want to allow users to fill out these forms.

Add a special mode to the editor page that only works when the page is a form for filling out that form.

No auto-save
No real-time collab, &c.
Cannot edit nodes, or add new ones
Cannot see version menu or node menus
Show submit and clear buttons on the bottom
When submitted, validate the data according to the field settings
Use the DatabaseAPI and its client-side classes for submitting form data
- Might need a bug in backend to handle permissions