Form: Not using a region any more as it was causing trouble in this
scenario with a Leaflet.popup.
Form: is now multipart/form-data and thus supports file uploads.
Form: new onSubmit hook to stop the form from posting with a
standard POST.
Form: using nested attribute names matching the Rails convention, e.g.:
spot[title]
spot.properties.name is now spot.properties.title
Giving the model Spot an urlRoot property so it can be sent without
being in a collection.