MS_DECOMP - Browaeys and Chevrot decomposition of the elasticity matrix.

Apply a decomposition of the elasticity tensor C, after:
   Browaeys and Chevrot (GJI, v159, 667-678, 2004)

[Ciso] = MS_decomp(C)
   Isotropic projection of the elastic tensor.

[Ciso,Chex] = MS_decomp(C)
   Isotropic, and hexagonal parts of the elastic tensor

[Ciso,Chex,Ctet,Cort,Cmon,Ctri] = MS_decomp(C)
   All parts of the elastic tensor

Notes:
    Output matricies are the partial components of the input elasticity
    matrix which maximise the norm of the high symmetry parts. This
    function assumes that C is in its optimal orientation for
    decomposition (use MS_axes to make this so).

References:
    Browaeys, J. T. and S. Chevrot (2004) Decomposition of the elastic
        tensor and geophysical applications. Geophysical Journal
        international v159, 667-678.