Migrate LIGO_LW XML I/O from glue.ligolw to python-ligo-lw

The glue.ligolw XML library is deprecated, this project should migrate the usage from glue.ligolw over to the new python-ligo-lw library. In the simplest circumstances, this may only require a search/replace of glue.ligolw ➡ ligo.lw, but that will need testing.