Com: Modified a useless comment
Add: the mopac-ddmc calculator. At this stage it is not finished
     and it cannot be tested because the mopac calculator is not able
     to read charge from the mopac output file.

Mod: The mopac calculator is modified in order to read the charge but it
     still does not work.
Mod: The mopac calculator is following the same structure as the others.