Gravity animation jitters

[fweiss]

It's OK when resting on a surface or when tipped up and rotated on the Z axis. When held flat in hand, it's very sensitive to slight tipping motion.

Maybe add a LPF to slow down the response time and remove noise.

[fweiss]

This makes it better:

• Motion timer from 200 ms to 800 ms
• framePeriodMiliis from the default 30 to 100

It's still haphazard in certain cases. Probably the IMU needs more LPF, just reducing the sample time doesn't seem to fully fix it.

[fweiss]

The remainder of the issue is passed on to #24