Addition of a PID listener (well, some implementation of it anyway)

This addition will allow PID compliant / OBDII readers to get information from our device.
Initial un-tested implementation of PID responder
Support for both ECU broadcast and direct comm to this ECU.
Updates to compile against newest canbus library

The canbus library was changed to include more functionality, be easier to use,
and generally be better. There are no longer RX and TX specifications for frames,
just one type. Also, many other things that CanHandler did are now in the canbus
library.
Another round of updates due to changes in canbus library.
Merge branch 'ArduinoDue' of github.com:collin80/GEVCU into WIP
Change how frames are received to match the new way the canbus library works.
Added const to definition of temporary arrays. This is required by GCC
> 4.7.0
Merge branch 'WIP' of github.com:collin80/GEVCU into WIP
Merge branch 'ArduinoDue' of github.com:collin80/GEVCU into WIP
Removed changelog since it never was synchronized to GIT very well anyway.

Anyone who'd like to know what changed should read the GIT commits for now. Eventually a real changelog should be written.