This adds support for keeping the uploads attached to a note when
deleting the same note. This is done by a simple checkbox that can be
clicked in the DeletionModal.
To do this, some parts of the note deletion had to be refactored,
especially in the case of the history page. Both the note deletion and
history removal methods used the same modal, which isn't applicable now
anymore. Additionally, there was a bug that the modal checked for
ownership in the frontend before allowing the note deletion. However, in
the context of the history page, the ownership couldn't be evaluated
since the backend API didn't include that information. This is now fixed
as well.
Signed-off-by: Erik Michelson <github@erik.michelson.eu>
