* talker_raw demo node

* use printf

* set quotes correctly

* talker and listener raw

* use only standard types

* rebased for ardent master

* more explicit demos

* reset talker listener to master

* make raw nodes classes

* address comments

* use serialization methods instead of manual serialization

* remove unused deps for test_msgs

* comparison size_t with unsigned int

* more verbose inline commenting

* rename to rmw_message_init`

* whitespace fixup

* address review comments

* warn unused

* raw->serialized

* suppress unused lambda capture warning on macOS

* use size_t (#243)