Suppressed change of disabled checkboxes.

This will make sense later.
Re-arranged form work flow (this should have no effect).
Disabled editing for special fields.

Because the application loads the previous document version from CouchDB for
every defined _id. I don't want the user to think, he could stage these
documents as new ones by unchecking the _id field selector.
The layout is kind-of a mess, to which I attend some other time.