When manually adding a dive, start with a simple dive

This is much friendlier than just showing an empty profile. I picked a
nice and simple three level dive. 25 minutes at 18m, 15 minutes at 9m, and
a safety stop.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
When adding a dive, make the final ascent slower

Simply trying to role-model safe behavior I guess. Fundamentally all this
should be configurable (so I added comments about that on the planner side
as well).

One of the interseting side effects of this implementation is that if the
user removes the safety stop and comes up directly from a deeper depth,
the slope of the ascent will change at 5m :-)

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Adding a dive changes the dive list

Duh.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>