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

Minor improvements in airframe config, param transfer / reboot are still not quite doing what we want

- 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

fixed runtime error with a typedef:
QObject::connect: Cannot queue arguments of type
'QSerialPort::SerialPortError'
(Make sure 'QSerialPort::SerialPortError' is registered using
qRegisterMetaType().)

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