this allows for 2 ways of controlling conflicts in the UAVCAN DNA
database. The first is to set CAN_Dn_UC_OPTION to 1, which resets the
DNA database, thus clearing any node conflicts.
The second is to set CAN_Dn_UC_OPTION to 2, which ignores node
conflicts in the DNA database
These options are useful for vehicles with UAVCAN smart batteries
where the node ID is fixed but the hwid changes and you want to do
battery swapping (possibly without rebooting)
AP_Arming tacks on the sub-system bit.
Remove PiccoloCAN's silly nullptr check
Require the library to supply the failure message (no default message)
Remove default cases so authors know to think about places they should
add things.