Fix a missed class name and update save_file()

Signed-off-by: Norv <a.w.norv@gmail.com>
Adapt prepare_file() and porepare_db().
(perhaps prepare_from_file() would have been better?)

Signed-off-by: Norv <a.w.norv@gmail.com>
ManageServer controller: refactor the code to handle settings forms.
Fixes. Tweak Settings to start instantiating it and use it normally.

Signed-off-by: Norv <a.w.norv@gmail.com>