Add method to write entire morphology class to file

[pdudenas]

Create a method that will save the morphology class to an hdf5 file. It should have the option to write everything (voxel data, config, optical constants) into the HDF5, or generate separate files. The former provides better portability and easier loading back into NRSS, while the latter maintains compatibility with CyRSoXS usage from the command line.