Simple sampling implementation for cartesian points.

This PR will have to be updated one #33 is accepted.  Also, this PR conflicts with #25.  This PR is simply to address a pressing need to perform sampling on Cartesian points.
The Cartesian robot class is a simple test class.  The robot "kinematics" are such that, Cartesian poses map directly to joint poses.  As a result, IK solutions are just a simple mapping from Pose(x,y,z,roll, pitch, yaw) -> Joint[].