Set better column widths in the dive list

This code seems rather crude to me. I'm sure this could be done better.

This also makes the column alignment work again.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Alternate background colors for dive list

This was written with massive hand-holding by Tomaz - actually, this was
mostly proposed via IRC by Tomaz and then implemented by me...

Right now because of the list-of-lists nature of the model we have the
small issue that every trip starts with a dark background dive, even if
the trip itself has a dark background.

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