Instead of only providing per(TimeUnit)
Useful for making conversion factors easier, eg `Inches.of(10).per(Rotation)` vs `Inches.of(10).per(Rotation.one())`
Update VelocityUnit.one() and VelocityUnit.zero() to return Velocity objects instead of generic Measure<? extends VelocityUnit<D>>; VelocityUnit is final, so the wildcard generic is unnecessary, and this makes the generated `per` functions possible for this type
Java generics are too limited to do what we need. This refactors generic code previously in Unit and Measure into unit-specific classes that can have unit-safe math operations (notably, times and divide) that can return values in known units instead of a wildcarded Measure<?>.
Unit-specific measure implementations are automatically generated by ./wpiunits/generate_units.py, which generates generic interfaces and mutable and immutable implementations of those interfaces. These make up the bulk of the diff of this PR (approximately 9300 LOC).
This also adds units for angular and linear velocities, accelerations, and momenta; moment of inertia; and torque.
