Backport NAV fixes to 2020.3.19

[hbeni]

Hi, is it possible to backport the current master branch NAV gauges back to the stable version 2020.3.19?

1. Fix #1359 (VOR/NAV gauges missing yellow ticks; needle center off) #1360
2. Fix NAV needle deflections #1467

It is currently not so easy to do radio navigation, because:
A) the needle rotation center is wrong
B) there are no yellow ticks, so selecting an OBS is relying on the feedback of the tooltip

[wlbragg]

Yeah, I can cherry pick this to our 2020.3.19 and ask Stuart to backport it to fgdata 2020.3.19.