Radio calibration fixes

- Fixes bug where function index was used instead of channel index causing incorrect channel reversal in some situations. The code only worked correctly if channel 0 was mapped to function 0 and so forth for other function/channels.This fixes Issue #886.
- Updated unit test to catch the above problem as well as better testing for channel reversal and function mapping.
- Updated UI so that channel widgets now show whether a channel is reversed or not.