HDF5 Read/Write Cellstr Example

Demonstrates how to write/read MATLAB cell arrays of strings as variable-length strings to/from HDF5 files. Example also demonstrates how to set up an unlimited-length dataset with chunking so that it could handle any number of elements in the cell array.

I didn't see any evidence of anyone doing this yet. I think any HDF5/MATLAB users have settled on using char arrays instead, which wastes space. Even the built-in hdf5write converts a cellstr to char array.