dive plan updates

[Dirk Hohndel]

The latest master has a few more changes to the dive planning.

We now include the plan in the dive notes (which makes it easy to print
it out with our existing methods) and include estimates of the gas
consumption during the dive, based on SAC rates that the user can enter
during the planning phase.

Still needed:

set the ascend speed
set the GFlow / GFhigh to be used for the plan, independent from the
overall setting
support CCR

/D