= power-cycle-safe calibration
- on power up, rx has control over servo immediately. apply the mixer (eg. delta/vtail) but do not apply stabilization (gyro/gain).
- calibrate imu only if it is still (over 100 consecutive unique samples).
- calibrate (rx) sticks only if they are still (100 consecutive unique samples).
- enable stabilization only after calibration is complete.
- led output to indicate calibration state
> 1 short (200ms) flash = rx calibrating
> 2 short flashes = imu calibrating
> 3 short flashes = both calibrating

= generate builds files
- RX3S_V1_20130119.hex
- RX3S_V2_20130119.hex

= some more naming and minor cleanups

= this new code exposed a bug in the rollover test. i think the old test tried to verify a non use case (where "t - last_t" the interval test > 2**31us, which should never be the case). i'll look into the rollover test again (perhaps all high order bits including the bit 31 ovf needs to be set)