Use two functions instead of a template

Use two functions instead of a template

Instead of a templated get_io_mode() function. Two functions have been defined:
- std::string get_io_mode();
- H5D_mpio_actual_io_mode_t get_io_mode_as_hdf5_type();

And the same for get_local_no_collective_cause() and get_global_no_collective_cause()