* add lc_extend_from_boundary in GUI

Bug fix to getNumMeshElements(unsigned*)

   1) this removes the asymmetry in all the routines involving mesh
      elements associated with points

   2) it makes it possible to use point-based datasets in the
      model-based post-processing module

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    PLEASE TEST --- ESPECIALLY THE INPUT/OUTPUT ROUTINES!
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* made GModel::getEntities() more efficient and generalized its use