Currently, the notes field uses a QTextEdit, which doesn't
send a signal if it goes out of focus. But for undo of
dive-editing we don't want to create an undo object for
*every* text change.
Thus, create a custom TextEdit widget that derives from
QTextEdit and turns the focusOutEvent into a editingFinished
signal.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
