comms/ProtocolNode: avoid using de-initialized (moved) objects, please
Sensor: fixed another misuse of move-construction
Some minor formatting corrections.
More minor changes intended to make g++ happy
comms/DataDeclarationBase: compiles with Clang again
comms/Message: placed header fields into child struct.

Yes, this is to make g++ happy: now we don't have to put the `packed`
attribute on Message itself and g++ won't complain about the non-POD
`body` field making it have to ignore that attribute.

The things I do for ...annoying compilers?  Hmm.
tests/live-test:  Reorganized, commented for better readability.
Fixes to transcoder-test re: moved Message header fields into child struct