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 is likely to change back to `http://localhost:8080/marmotta/`, because it applies only to my local build.

Sooner or later we should change the whole suite to run the ldp endpoint at a suitable root URL for our resources (`http://api.dp.la/`?).