Support @list and compound literal compaction

[rubensworks]

Currently, this serializer will not output RDF lists via the @list keyword by default, and compound literals for RDF direction.
Because of this, this serializer does not pass all of the JSON-LD 1.1 spec tests.

A special buffering mode could be added to this serializer that would buffer all potential list and compound literal triples, and emit them at the end of the stream if they are valid.

Obviously, this would lose some of the streaming benefits of this serializer, but it may be still valuable for some use cases.