mavproxy_soar: Add initial soaring display

[Ryanf55]

Purpose

Add an initial soaring module, which displays the location and estimated radius of the thermal from AP's thermal soaring estimator.

Once we have a mavlink packet definition for the thermal estimator, we can move to that from NAMED_VALUE_FLOAT.

Demo

Terminal 1:

./Tools/autotest/autotest.py build.Plane test.Plane.Soaring --map --speedup=1

Terminal 2:

mavproxy.py --console --master tcp:127.0.0.1:5763 --map
module load soar

Once the vehicle hits the thermal southwest of home, it will show up on the map. You can see the estimator converge on the thermal.