CAN header construction fix.
CAN header construction fix.

1. Updated mapping for population of CAN header fields to be correct.
2. Updated identifier names to more concise, as they map between CAN
header fields and hardware registers.

UASLab/dspic33-servo-can-node.X,SenteraLLC/dspic33-servo-can-node.X,SenteraLLC/dspic33-servo-can-node.X,UASLab/dspic33-servo-can-node.X