Show the dives as a gtk list/tree widget

Show the dives as a gtk list/tree widget

Ok, so I'm not very good at this.  I'll need to enclose the dang thing
in a scrollable window, and then make that scrollable thing just part of
the whole window.

But hey, it's pixels on the screen.  Pixels that show the names of the
dives we've parsed.  At least as many as will fit on screen at one time ;)

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>