Make the dive list start as a plain notebook page

Make the dive list start as a plain notebook page

I've been wondering how to make 'subsurface' work better on a small
screen (I used to travel with a crappy netbook - I may have upgraded my
laptop since, but it is still a design goal of mine to make sure it all
works fine in that kind of environment).

And ever since the dive list was made much wider and moved below the
notebook, it's annoyed me how much room it all takes if I want to have
both a reasonable plot window and several dives visible at the same
time.

The solution seems to be to just make the dive list be a notebook page.
That makes the default layout very dense.

At the same time, when you have the pixels, it's horrible, because you
would want to see the dive list and move between dives while at the same
time also seeing the dive profile change.  But that is solvable by
simply making the dive list notebook page be detachable, so if you have
a nice big screen, just detach the dive list page and now you have
independent windows for the dive list and the dive info.

NOTE! I don't have any way to re-attach the dang thing.  I think I'd
need to learn about drag-and-drop targets etc.  So once you've detached
the dive list, it stays detached.

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