Only define RUNPARALLEL if MPI support is enabled for HDF5
Fix the configure option for Szip in HDF5 EB. It is actually --with-szlib instead of --with-szip
New EasyBlock for HDF5-serial

This EasyBlock allows to compile HDF5 without MPI support.
It is necessary to create a new EasyBlock because the HDF5 one relies on the 'usempi' option thatr requires an MPI-enabled toolchain.
Merge branch 'develop' of github.com:hpcugent/easybuild-easyblocks into hdf5-serial
Remove the HDF5-serial easyblock, and update the HDF5 easyblock to allow build with non-MPI toolchains
Merge branch 'bugfix_hdf5_eb' of github.com:besserox/easybuild-easyblocks into hdf5_besserox
Merge branch 'hdf5-serial' of github.com:besserox/easybuild-easyblocks into hdf5_besserox
avoid code duplication, consistently use .get('usempi', False)
stop using self.toolchains.options['usempi'], use self.toolchains.options.get('usempi', None) instead
Merge pull request #301 from boegel/hdf5_besserox

enable serial HDF5 builds and use correct configure option for Szip