add routine to parse between LALDictSequence structure and XML-type datafile
requested to merge wanting.niu/lalsuite-jolien-rebased-master:new-injection-format into new-injection-format
We write a xml-parser that can convert between the new CBC injection structure (LALDictSequence) and GstLAL's XML-based datatype. This parser can also be used as a path to the conversion between HDF5 and XML.