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 Convert the standard orbital element set into an Alfriend orbital element set 
             [a,i,W,w,e,M]           ->           [a,th,i,q1,q2,W]
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   Form:
   ela = El2Alfriend( el, nu )
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   ------
   Inputs
   ------
   el            (:,6) Standard orbital element set [a,i,W,w,e,M]

   -------
   Outputs
   -------
   ela           (:,6) Alfriend orbital element set [a,th,i,q1,q2,W]
                          where:   th = true latitude
                                   q1 = e*cos(w)
                                   q2 = e*sin(w)
   
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