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.

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

still some remaining issues with pending line items bouncing back from
data model