ESC status feedback

Publishing ESC status data to the ORB topic `esc_status`.

Assuming the following units of measurement:
* esc_voltage - 100mV per LSB
* esc_temperature - 0.1 degC per LSB
Ok, fair enough. I think we have to revisit our style guide (which in turn is based on NASA and JSF style guides). My gut feeling is that the intention of the MISRA designers are fine, but doing it like this only works safely if -Wconversion and -Werr is on. The reason being that if we e.g. upgrade a float to a double for a variable inside the cast, the explicit cast introduces an unexpected loss of precision. This is only safe if -Wconversion is on and produces an error, because the consequences of the change become visible.