Also move default component ID into data model

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

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

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

fix pending items indicator