Configure libhdf5_serial if it's available

Changes proposed in this pull request

Configure libhdf5_serial if it's available and libhdf5 is not. This happens, for example, by default on Ubuntu.
Change configuration of HDF5 support so that specifying hdf_include or hdf_libdir does not change the state of hdf_support from 'n' to 'y'

If applicable, fill in the issue number this pull request is fixing

Closes #1718

Checklist

[X] The pull request includes a clear description of this code change
[X] Commit messages have short titles and reference relevant issues
[X] Build passes (scons build & scons test) and unit tests address code coverage
[X] Style & formatting of contributed code follows contributing guidelines
[X] The pull request is ready for review

Cantera / cantera