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.
Marmotta doesn't seem to implement a truly idempotent `PUT`, which isn't perfect, but may just be the shape of what we're up against.  In any case, idempotency of `Harvesters` might not be affected.