Split M2ulPhyS::restart_files_hdf5 into multiple functions (#244)

This is an intermediate commit.  The idea is to extract the most of
the read and write functionality from M2ulPhyS::restart_files_hdf5
into separate functions.  In the previous state the read and write
code were intertwined, which made it difficult to understand.  The
eventual goal is to move the parts that are generic into
IODataOrganizer (and related classes), in order to minimize the
restart read/write code within M2ulPhyS, which should make it easier
to reuse these capabilities for other Solver types down the road.

src/M2ulPhyS.hpp

@@ -345,6 +345,8 @@ class M2ulPhyS : public TPS::Solver {
 
   // i/o routines
   void restart_files_hdf5(string mode, string inputFileName = std::string());
+  void write_restart_files_hdf5(hid_t file, bool serialized_write);
+  void read_restart_files_hdf5(hid_t file, bool serialized_read);
 
   void Check_NAN();
   bool Check_JobResubmit();