Add "add dive(s) to trip above" feature

This honors the sort order of the dive list when figuring which trip is
"above". It works both on a single dive or all selected dives.

This also fixes a couple other cases where the dive list selection and
trip display could get messed up.

Fixes #287

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Removed the ugly icons on the visual profile editor

Removed the ugly icons on the visual profile editor and replaced them with
the much better looking ones that Luisa designed.  This was not a simple
search and replace since Luisa's design was a bit more sophisticated.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>