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.  
the function name can be confusing, because "active" is already used to tell if some stuff is included in simulations or not, e.g. active and inactive elements. how about naming those nodes as "non-ghost nodes" or "intrinsic nodes" or something else?