Methods for properties; refactoring

2013-05-31
- added methods for properties

2013-05-27
- fixed ontoTree so to include OWL.Thing
- added alpha sorting to __buildClassTree
- split ontologyURI() and ontologyPrettyURI
- modified __ontologyURI so to include DC.identifier metadata
- updated ontologyAnnotations method: now multiple annotations are
returned correctly
- added ontologyPhysicalLocation property