Mex for geometricJacobian and findKinematicPath

* Wrote a mex version of geometricJacobian (and findKinematicPath, which geometricJacobian uses), so that we can use it for task space control on Atlas. 
* Moved tests that were in examples/Atlas to a better place, and updated them so that they compare Matlab vs. mex.
* geometricJacobian in C++ currently uses drakeJoints, so I'm conditionally compiling on Windows. However, the mex version is used by default if use_mex is not passed into geometricJacobians, so the test will fail. I don't want to check for existence of a mex file in Matlab geometricJacobian though, for performance reasons. Of course, really I need to get drakeJoint stuff to compile under Windows, but what do you think is the best solution for tomorrow?
* note that the floatingBase implementation of geometricJacobian will rely on a different format of kinsol, so I'll have to rewrite it later. Still, the findKinematicPath function will be useful later as well.
Yeah, I'll have to discuss with Russ where to put these.