CModernMaterialPropagationManager(MaterialManager, Envelope)
  calculates the propagarion (Kz) matrix.
 
  Old description:
    Theta and phi are the angles from the optical axis,
    therefore phi is miningless for uniaxial crystal.
    Moreover this is good from the point of view of
    polarization because one is always along x and other along
    y. Therefore if you want something different you need to
    manipulate the pulse wavevector intensity distribution.
 
    For birefringent crystals provide:
    fReferenceTheta, fReferencePhi (only biaxial) - the angle between the
    kx, ky=0 vector and the optical axis (usualy kx, ky = 0 is the propagation
    direction)
    iRefractiveIndexID - if not set two polarizations are managed, if set,
    calculates only one polarization, 'o', 'e' for uniaxial and, 'h', 'l',
    for biaxial crystal ('h' = higher value of refractive index, 'l' =
    lower value of refractive index).
 
    assumption: in case of uniaxial crystals, the 'o' is always along 'y'
    and 'e' is along 'x', one has to do the polarization splitting with
    another tool