relax SVN archive

Created the ResidueList.from_xml() method.

Created the MoleculeList.from_xml() method.

Added a test to xml_read_element() to check if the pipe is empty.

Created the RelaxFromXMLNotEmptyError class.

Changed the call from MoleculeList.xml_read_element() to MoleculeList.from_xml().

Wrote the PipeContainer.xml_read_element() method.

Wrote node_value_to_python() to convert the XML nodeValue to a python object.

Created xml_to_object() to place the contents of an XML element into a python container.

Renamed PipeContainer.xml_create_pipe_element() to PipeContainer.xml_create_element().

Wrote the Relax_data_store.xml_read() method.