Adding universal read_var_names() interface.
Removing read_elemental_var_names(), read_nodal_var_names(), read_global_var_names().
Renaming num_globals -> num_global_vars.
Make the initialize_xyz_variables() interfaces the same.
Adding universal write_var_names() interface.
Replacing explicit calls to ex_put_var_names() with unified interface.
Also wrap the call to ex_put_var_param() in write_var_names().
Return if no global variables to write.
Return if no nodal variables to write.
Adding _nodal_vars_initialized flag.
Adding ExodusII_IO_Helper::check_existing_vars().
Using check_existing_vars() function.
All the new helper functions should be private.
Merge branch 'exodusII_refactor'