Velocity Tracker II: The Revenge of Velocity Tracker

Bug: 5265529

Rewrote the velocity tracker to fit a polynomial curve
to pointer movements using least squares linear regression.
The velocity is simply the first derivative of this polynomial.

Clients can also obtain an Estimator that describes the
complete terms of the estimating polynomial including
the coefficient of determination which provides a measure
of the quality of the fit (confidence).

Enhanced PointerLocation to display the movement curve predicted
by the estimator in addition to the velocity vector.

By default, the algorithm computes a 2nd degree (quadratic)
polynomial based on a 100ms recent history horizon.

Change-Id: Id377bef44117fce68fee2c41f90134ce3224d3a1