[x] show final approach of FW landing pattern on flight map (carry over from #27)
[x] calculate landing pattern from landing angle
[ ] show probable landing area around land point
[ ] wind considerations? (possibly more on pixhawk side)
[ ] show small arrow indicating direction of loiter circles
[ ] default acceptance radius in loiter-to-alt simple edit mode to zero, and don't show it on the editor. Only the FW landing pattern complex mission item will use the LOITER_DOWN option, which uses this acceptance radius.
TODO