Support gps coordinates for the location info

Sadly, no way to show them yet.  But it would be nice to let people
enter them (and it would be doubly nice to have a dive computer that
does it at the surface), and then perhaps just do the "point browser at
google maps" thing.

Saving/parsing tested by hand-feeding the location of Enenui (Molokini
Crater) from google maps by hand into my divelog.

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