EulDot2Rates:

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   Converts 3-2-1 Euler angle rates into angular velocity. If only one
   input is given, the output is the transformation matrix.
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   Form:
   w = EulDot2Rates( e, wEul, n )
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   ------
   Inputs
   ------
   e		 (3)    Euler angles
   wEul (3)    Angular rates
   n    (1)    Orbit rate (for rotating frames only, optional)

   -------
   Outputs
   -------
   w	   (3)    Euler angle rates

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   Reference: Hughes, Spacecraft Attitude Dynamics (1986), Eq. 25 p. 27
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