Feature suggestion: 3 stage nitrous

[mb300sd]

This seems to be a feature of some controllers that would be really easy to implement. I'm only half way running on MS right now, but I'd definitely like to see it in the future.

1: solenoid 1 on, 2 off - 50hp shot
2: solenoid 1 off, 2 on - 100hp
3: Both on - 150hp

Probably want to add a delay feature between 1/2 to make sure 1 is fully off before 2 is on to prevent leaning out.