feature, add Newmat support for HDF5 I/O

[steven-varga]

Add h5cpp I/O integration for Newmat C++ matrix library.\n\nTask:\n- Vendor Newmat headers into thirdparty/newmat/\n- Create h5cpp/H5Mnewmat.hpp\n- Add example examples/linalg/newmat.cpp\n\nAcceptance Criteria:\n- [ ] Newmat Matrix writes to HDF5 and reads back correctly