Forced each message to have declared type as parts of Bus logic
depends on it and previously we encountered undefined
behaviours. Added tests and messages validators.
The system watchdog monitors whether there is message traffic
on the Bus. If no message was sent for an extended period of time,
a reset will occur. It should also protect against system-wide hangs.
On Linux, watchdog is simulated by a FreeRTOS task that will call exit
on timeout.
