modified from_xml to read thesaurus title in the form title, version
implemented inspire to_xsd function
added more from_xml tests and fixed error when reading wrong thesaurus name in from_xml
Merged with smanousopoulos/master (INSPIRE XSDs, tests)
Renamed tests for INSPIRE XML serializers
Reviewed INSPIRE XML serializers (to_xsd()). Must fix XSD paths.
Rewrote key-tuple serializer (accepts a prefix)
Minor fix at key-tuple serializer (accept non-empty prefix)
Fixed #37