Completed hover effector unit test.

Task @T26 : Completed hover unit test. Unit test is accomplished by
hovering an object set at 1 meter altitude for ten seconds, then
checking the min, max, and average altitudes for the last one
second period. There are three runs, one starting at set point, one
1 meter above and the last 1 meter below to test the ability to
capture and stabilize. In all cases the average altitude must be held
to < %1 devation to pass, and the extremes must be < 4% (< 2% when
started from set altitude). This is ready for review and merge.