Maintain the selection when aborting "dive add"

We remember what was selected before and restore it. Maybe there's a more
"Qt way" of doing this, but my implementation appears to work :-)

Also remove unconditional debug output that snuck into an earlier commit.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Handle tank data correctly in profile editing mode for manually added dive

This is subtle. Normally you would expect someone to edit the tank data by
simply clicking on it in the equipment tab. But a user could conceivably
edit the tank data after clicking on the profile editing button instead.
This works now as well.

This also addresses the issue that start and end pressure were not shown
in profile editing mode.

Fixes #235

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>