Planner: use the actual setting for GF low at max depth

Using the default_prefs value makes no sense.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Planner: reset GFlow and GFhigh when we're done

While planning we might change the gradient factors. Make sure they are
back to what's in the preferences when we're done planning.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Planner: show the GF used for planning on top of the profile

Showing the GF in the preferences is just confusing.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Planner: don't reset GF when preferences change

The planner has its own view of the gradient factors. So replacing those
with the ones set up for viewing dives in the preferences is wrong.

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