Support of CalcHep model files with two dark matter candidates
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For this purpose, two new options to MakeCHep[] have been added:

1) DMcandidate1; values: "Default" or "Symmetry==Value"; default value: "Default"
   - With "Default" the DM candidate is identified as before: 
     all particles odd under the first Z_2 defined as global symmetry
   - For another choice, one can give first the name of the global symmetry and then 
     the quantum numumber; for instance "Rparity==-1" would return the same result 
     for SUSY models where the dark matter candidate is the LSP
   
2) DMcandidate2; values: "None" or "Symmetry==Value"; default value: "None"
   - If a second DM candidate should be included, the condition is given in the same way 
     as non-standard DM candidates in the case of a single DM candidate.

Example (see also the Model SDDM):

One can consider a Z_4 symmetry 

  > Global[[1]] = {Z[4], Z4};

and two fields with different charges under the Z_4:

  > ...
  > ScalarFields[[1]] =  {H, 1, {Hp, H0},     1/2, 2,  1,1};
  > ScalarFields[[2]] =  {S, 1, ss,     0, 1,  1, Exp[2*Pi*I/4]};
  > ScalarFields[[3]] =  {H2, 1, {HIp, HI0},     1/2, 2,  1, Exp[2*2*Pi*I/4]};

Note, Z-symmetries are always taken to be multiplicate symmetries!

To get ss and HI0 as DM candidate, run 

  > MakeCHep[DMcandidate1 -> Z4 == -1, DMcandidate2 -> Z4 == I];