Persist OriginalRecord

This is a substantial rewrite of OriginalRecord to allow them to persist to LDP.

This isn't mergeable until the forthcoming Marmotta `3.3.0` release and a corresponding update to `marmottawrapper`.  Until then, I submit it for sanity check.
This might be an overly stringent definition of `==` I'm very open to comment  on this. See http://www.skorks.com/2009/09/ruby-equality-and-object-comparison/ on equality operators in Ruby.