Rename internal Binary interface to BinaryValue

There are two ModeShape-specific Binary interfaces: org.modeshape.jcr.api.Binary (which extends javax.jcr.Binary) and org.modeshape.jcr.value.Binary (which extends org.modeshape.jcr.api.Binary). The former adds some very useful methods for accessing the SHA-1 hash and the ability to get the MIME type, and are things we do want to expose to client applications via our public API. The latter contains things (include the BinaryKey concept) that are used internally and should not be exposed; however, the internal Binary interface should probably be renamed to BinaryValue to make the distinction more clear.