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   Compute the plume forces and torques on a set of elemental areas.
   While designed for far field calculations it uses z buffering to 
   insure that mass is conserved.
   This routine works in the metric system!!!!
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   Form:
   [f, t] = Plume( thrust, rREA, tREA, uREA, gREA, normal, r, area, tArea, angInf, sigma )
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   Inputs
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   thrust        (m)   Rocket engine thrust (N)
   rREA          (3,m) Vector from c.m. to the rocket engine (m)
   tREA          (m)   Chamber temperature of the thruster
   uREA          (3,m) Thruster unit plume vector
   gREA          (m)   Ratio of specific heats for the gas
   normal        (3,n) Surface normal vector
   r             (3,n) Vector from c.m. to the panel center (m)
   area          (n)   Elemental area (m^2)
   tArea         (n)   Average surface temperature
   angInf              Plume turning angle at infinity (usually near ¼/2 rad);
   sigma         (2)   Surface accommodation coefficents
                       [normal, tangential]

   -------
   Outputs
   -------
   f		      (3,m) Force vectors 
   t		      (3,m) Torque vectors 

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