Add canonical and tuple identifiers to output

[gaurav]

We currently only provide concept identifiers as URLs (e.g. NCIt C799). We should also provide concept identifiers as tuples (i.e. (NCIt, C799)) and as a canonical URL (http://ncicb.nci.nih.gov/xml/owl/EVS/Thesaurus.owl#C799) in order to facilitate mapping to other resources. We could also include the permissible value public identifiers (timsbiomed/cadsr-on-fhir#4) for elements that don't map to an NCIt concept.