Class for parallel reading of partitioned mesh data

Along with commit 4cda158,  member function ``stop()`` of class CPUTime and RunTime were removed, and the calling of the function has been removed in the related files.  
Removed it. In future, we may not have an option of ``ÒGS_USE_MPI`` but  other option named for  MPI/DDC related stuff. For those commonly used MPI relates classes, a preprocessror ``USE_MPI`` is enough.