Speed up CMM computation, add Euler angle support to forwardJacDot

CMM: implemented a recursive algorithm in matlab/mex for computing centroidal momentum matrix (CMM). 15x speed improvement for Atlas using the mex implementation over the previous version which required a matrix inverse. passes relevant unit tests.

Jdot: added roll/pitch/yaw support for Jdot computations. relevant drake unit tests pass. added a case to testMex to make sure matlab/mex functions are consistent. Since we don't yet have dJ implemented for rotations, I didn't add a test case in testForwardJacDot (but I'm confident in the values coming out based on walking controller performance in my DRC branch).