* New in-memory implementation (by Paul),
* Split out NodeFactory into TripleFactory and GraphElementFactory.
* Added Container (Bag, Alternative and Sequence support) and Collection
* Added visitor pattern for typed nodes (URIReference, BlankNode and
I found the exact details of Bag, Alternative and Sequence and the issue of list elements versus "_1, _2, ..." a little confusing. For example, Bag and Sequence both have the phrase "possibly including duplicate members" but Alt doesn't include a similar phrase. The description of Alt suggests it doesn't support duplicates, I hope I got it right.