Add shorthand actions for showing just one of the panes

Add shorthand actions for showing just one of the panes

Currently just tied to F1-F4 (for divelist, profile, info, and "all
three" respectively), which is just crazy.  But using "ctrl-P" for
"Profile" isn't sane either, that's the standard printer keyboard
shortcut.  So what would be good keyboard shortcuts for these things?

I also wonder how I can get gtk to shut up about the fact that a pane
becomes too small for the contents of that pane? We very much want to do
that, and it's very intentional.  Gtk does the right thing apart from
the whining (and apart from the visually ugly part of a widget that
doesn't fit, but making it pretty doesn't really seem possible).

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