First HDF5 release

In this release, RH 1.5D the file format for both input and output is changed from netCDF to HDF5. This means that it only requires one external library: HDF5 (instead of requiring both netCDF4 and HDF5). Because netCDF4 is built on top of HDF5, the latest change is backwards-compatible: old input files still work with RH, and new output files can still be read by the same tools (mostly).