USB VCP Cli (#237)

* Core: ring buffer.
* Api: usb vcp. F3: vcp glue code.
* Applications: cli draft version.
* Cli: basic working version, includes help and version commands
* HAL: vcp on f2
* Makefile: update openocd conf
* F3: vcp rx with freertos stream
* Cli: help
* Cli: standard commands, api-hal-uid
* Power: cli poweroff.

make/rules.mk

@@ -73,7 +73,7 @@ upload: $(OBJ_DIR)/upload
 debug: flash
 	$(DEBUG_AGENT) & echo $$! > $(OBJ_DIR)/agent.PID
 	arm-none-eabi-gdb \
-		-ex "target extended-remote 127.0.0.1:4242" \
+		-ex "target extended-remote 127.0.0.1:3333" \
 		-ex "set confirm off" \
 		-ex "source ../debug/FreeRTOS/FreeRTOS.py" \
 		$(OBJ_DIR)/$(PROJECT).elf; \