Support extended CAN frames (29-bit IDs).

The CanMessage, CanMessageDefinition and AcceptanceFilterListEntry
structs now have a CanMessageFormat attribute, which indicates if the ID
should be sent or received as a standard or extended ID. For incoming
message requests, we automatically select the format based on the value
of the ID (i.e. greater than 0x7ff is automatically extended).

Fixed #197.
Merge branch 'next' into iso

Conflicts:
	src/can/canread.cpp
	src/can/canread.h
	src/can/canutil.cpp
	src/can/canutil.h
	src/can/canwrite.cpp
	src/platform/lpc17xx/canwrite.cpp
	src/platform/pic32/canread.cpp
	src/platform/pic32/canwrite.cpp
	src/signals.h
	src/tests/canread_protobuf_tests.cpp
	src/tests/canread_tests.cpp
	src/tests/canutil_tests.cpp
	src/tests/canwrite_tests.cpp
	src/vi_firmware.cpp