Add Frenet-Serret Frame Predictor plugin

[make-42]

I wrote this little plugin to trade a bit of added jitter/jaggedness for predicting a few reports into the future for tablets with a bit of latency.

• First it'll get the last few reports from your tablet
• Then it'll fit a cubic B-spline through them to smooth them out
• Finally it'll compute tangential and normal acceleration over that timespan in a Frenet-Serret reference frame linked to the cursor and its past trajectory (pretty much just determining direction of movement and signed curvature).
• Then it'll compute a average of the derivatives of those accelerations over that period giving more weight to the recent samples.
• Then it'll just integrate with those derivative values to compute a prediction of where the Frenet-Serret frame should be at a set offset in the future.

Perceived latency goes down...