hdf5_ep

[svn-r24615] Feature: HDFFV-8336
Changed to use the quick steps described in INSTALL_CMake.txt.
Previous version is available by --old.
Added a help page to explain how to use.
Added a fix to figure out the current HDF5 version and use that to find the
correct file for install. (Still need to figure out the platform name.)

Tested: Jam and Platypus. Both failed in the installed steps because
the Cmake produced HDF5-1.8.13-Linux.sh even though the version number is
1.8.13-snap3.  Committed it so that Allen can fix the version number error.