AmbSignalMaper: Implement dbc2amb

AmbSignalMaper: Implement dbc2amb

Adds a "Direct Workflow" for generating CAN plugin from *.dbc file without
intermediate *.json file. dbc2amb selects signals from *.dbc file according to a pre-defined *.msg file which doesn't change when *.dbc file changes. This avoids repeating manual steps on *.json file.

May be useful at very early and late stages of vehicle software development, when there are many changes (cosmetic or other)  to *.dbc files.

TODO list:
* implement "mixing" of multiple *.dbc files into one plugin
* allow manual specification of message composition in *.msg file
* implement handling of SEND in addition to RECEIVE