add annotation for matches and synonyms

[wdduncan]

It is helpful to be able to relate terms to terms (having IRIs) in other ontologies. skos provides the properties:

• skos:match
• skos:exactMatch
• skos:broadMatch
• ect.

Sometimes it helpful to relate a term to words/expressions the have similar meanings. The oboInOwl (http://www.geneontology.org/formats/oboInOwl#) namespace provides the following annotations:

• oboInOwl:hasSynonym
• oboInOwl:has_broad_synonym
• oboInOwl:has_narrow_synonym
• etc.