Activate forms setting3

Makes the "downloadable" Xform field actually work to prevent submissions, as well as downloads, of surveys. This is consistent with the on-screen label for that switch as "Form active".

Also increases user friendliness of the form by placing all controls in showed boxes, so that the groups of settings are more obvious.
Adds a "submit" button for the boolean settings (replacing a toggle action).
Removes pretty, but misleading label buttons.
Adds a "Return" button so that the home screen will be refreshed and therefor reflect the changes made on this screen.

Inactive forms return status code 404(Not Found) -- in keeping with the behavior of ODK Aggregate.