0022172: [CEA 790] create the groups corresponding to domains

0022172: [CEA 790] create the groups corresponding to domains

1) Do not erase "mesh.Compute()" command if the next command
   "[ group1, group2 ] = mesh.GetGroups()" dumps groups created by some algorithm.

2) Clear "mesh.RemoveGroup( group )" command
3) Clear "[ group1, group2 ] = mesh.GetGroups()" command if the groups
   are removed later.