The download already worked, but we didn't display the new dives. This
introduces a new slot for MainWindow that updates what is displayed in
Subsurface after files were imported.
With this change we can successfully download ONCE - but when trying to
download a second dive the dialog doesn't appear to get refreshed the
right way - the OK button doesn't appear to work anymore (Cancel however
does).
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>