UI Improvements Accumulator

A list of items that do not require a separate item, but would be otherwise forgotten * [ ] Transmitter battery voltage on main screen >10.0V is not centered and overlaps the circle * [ ] Voltage calibration seems to have mistake formatting as 00.0 meaning at least two digits before decimal, one after decimal. Would be very good to allow 0.00 so that more precise calibration can be set * [ ] EXT Vol is a bit jarring. Maybe go away together with #15