This method was only doing half of the job, namely adding subsolutions
to the message fields. However, the start_scene was not yet written.
This was handled manually in some but not all callers.
To avoid this inconsistency, the new method toMsg() takes care of both
actions now, while the old fillMessage() method was renamed to appendTo().
Probably the most invasive format patch, also changing some internal API.
I deliberately disabled ClassCase and MethodCase checks for the moment
to avoid public API changes in this patch set.
Previous code was generating the error on changing object_name in config/panda_config.yaml file because of this bug as here we are overwriting the object_name as "object" which brought the inconsistency in code.