This is for XML formatted relax state and results files. The implementation was complicated as a
special data_store.data_classes.RelaxDictType object with to_xml() and from_xml() method has been
introduced to handle custom dictionary-type objects.
The cdp.nmrglue object is the data_store.nmrglue.Nmrglue_dict object which inherits from the
RelaxDictType object. This has elements set to data_store.nmrglue.Nmrglue instances. This Nmrglue
object inherits from data_store.data_classes.Element, however the to_xml() and from_xml() methods
have been copied and modified for this special object. This Nmrglue container has three main
attributes, the nmrglue dic, udic, and data objects.
The Nmrglue to_xml() and from_xml() methods handle the 'data' object by encoding and decoding it in
the Base64 string format. All the other objects are handled by the fill_object_contents() or
xml_to_object() functions of lib.xml.
