Read new Bilby hdf5 format

We recently changed how Bilby result files are written to hdf5 (deepdish is incompatible with recent versions of pandas so we ditched it), see bilby!925 (merged). It's quite possible that the new format will be incompatible with pesummary.

There are still some bugs to be worked out in the implementation so the current version isn't final, but we will want to make this the default for GW analyses. Notably, bilby_pipe currently can't write this format so that will need to be done before we move onto pesummary.