Reconcile ontologies from Fedora3, hardcoded in baseline, and this Ontology repository

Resolves: https://www.pivotaltracker.com/story/show/50895969
* Changing namespace URIs and size/digest predicates to match RdfLexicon, adding other properties from RdfLexicon and fcrepo3 rels-ext ontology
* Changing namespaces of RELS-EXT properties
* Changing namespace to http://fcrepo.org/ontology and adding owl:sameAs links to old RELS-EXT info:fedora URIs for backwards compat
* Separating repository, rest-api and relations into three separate ontologies