create general purpose c/c++ version of Firmata.cpp

[soundanalogous]

Currently, code within Firmata.cpp directly calls many Arduino-specific functions. Create a Firmata base class that is purely c/c++ that can be hosted outside of /firmata/arduino and used therefore easily used for any c-based Firmata client.

For backwards compatibility (since many existing Arduino sketches include "Firmata.h"), the purely c/c++ version would have to be named something like FirmataBase. On the Arduino side, Firmata would either wrap or extend FirmataBase to include Arduino-specific functionality. Likewise for c-based Firmata clients or even non-Arduino architectures.

[zfields]

I'm putting together a prototype for this work item.

[soundanalogous]

Done via #313.