remove duplicate jcrRdfTools and unused session accessor in RDF iterators
remove unused pid-function-factory method from minters
remove unused function and input iterator-traversing ZippingIterator
remove vestigal String constant from abandoned ATOM-JMS impl
document a temporarily unused constant in RdfLexicon
Merge pull request #611 from fcrepo4/describes-predicate

Use IANA describes/describedby predicates to link a non-rdf source and its description
Merge pull request #612 from fcrepo4/80959252

Remove dead code

Related to: https://www.pivotaltracker.com/story/show/80959252
Add MultiPrefer type and action to handle multiple Prefer header requests

Resolves: https://www.pivotaltracker.com/story/show/81242476
Use message/external-body MIME type for registering 'redirect' binaries