MS_brow_chev_norms

Calculate the percentages of the original matrix norm represented by the
individual decompositions of an elasticity tensor.
See Browaeys and Chevrot (GJI, v159, 667-678, 2004), and function
   CIJ_brow_chev_decomp()
[P] = CIJ_brow_chev_norms(C,Ciso)
   Isotropic part (scalar)
[P] = CIJ_brow_chev_norms(C,Ciso,Chex)
   Isotropic, and hexagonal parts of the elastic tensor (vector)
[P] = CIJ_brow_chev_norms(C,Ciso,Chex,Ctet,Cort,Cmon,Ctri)
   All parts of the elastic tensor (vector)