soy.atoms.Axis and Body.rotate function

[DavidCzech]

We need an atom class called Axis storing the three axis values ODE takes for various functions (joints, rotating a body, etc)

Testing should be done to ensure the three values constrain to ODE's specs and a cdef function should return a dReal[3] for internal use.

Lastly, adding a function to soy.bodies.Body such as .rotate which accepts an axis and angle, applying these to dRFromAxisAndAngle, or axis or two axis arguments to dRFrom2Axes, or None for both which sets the body's rotational identity.