New EasyBlock for HDF5-serial

This EasyBlock allows to compile HDF5 without MPI support using a toolchain with no MPI.

It is necessary to create a new EasyBlock because the HDF5 one relies on the 'usempi' option that requires an MPI-enabled toolchain.

Note: this easyblock already includes the bug fix for HDF5 suggested in https://github.com/hpcugent/easybuild-easyblocks/pull/286