Trip location and notes

[Dirk Hohndel]

Small behavioral change

When the user selects exactly one trip (usually by clicking on the trip
header or using the cursor up/down keys), then the Dive Notes change;
they now display just trip location and trip notes - and just like with
a regular dive they can be edited in place.

As a small piece of trivia - this not only implements a feature we had
in the Gtk version (editing trip location and notes), it actually adds
something we never had... I somehow never got around to actually SHOW
the trip notes anywhere. You could edit them, they were saved in the XML
file, but they were never shown...

Please play with it and poke holes in my logic!

/D