Fixed race issues in config upload, tested to be reliable now - board startup scripts now need the other half of testing

Instantiate a PX4 config view in PX4 mode from start, since boards with just the bootloader (or no working telemetry) cannot be flashed else.

don't process updates to unmapped rc channels when we're not in
calibration mode

- minor refactor of airframeconfig.cc
- add placeholder for new scratch build multirotor

Add "skip" buttons in msg box (instead of cancel); allow user to cancel
upload of rc params after reviewing them

Add persistRcValuesButt to allow mappings to be persisted outside the
calibration mode; cleanup const params in param dataq model;  add some
debug for mapping problems

Checkpoint: RC calibration much better / operation, can use UI tweaks. Airframe config in, but not operational and still very functional / ugly.

when param widget is loaded we only want to re-request the whole param list if we don't already have one