hdf5_ep

Merge pull request #280 in HDFFV/hdf5 from develop_merge_cache_image_09 to develop

* commit '70d66452467d5cf40df31604cf2e3ebfc1d67acd':
  Optimize loading cache image, removing lots of memory allocations and copies.
  Simplify H5C__serialize_single_entry(), using H5C__generate_image()