Improve LED interface

[maksimdrachov]

There should be some differentiation between whether it has successfully transmitted or received a CAN frame.

One blink = succesfully transmitted
Two blink = succesfully received

[pavel-kirienko]

This won't work in practical networks because you wouldn't be able to tell if it's two transmitted frames one one received frame. This is why we have separate RX/TX LEDs in FluxGrip, and why we should have done the same here. I am going to open a new ticket that will supersede this.