Remove repeated shutdown() method from TransactionalGraph. #479

As shutdown() is defined in Graph having it in TransactionalGraph is redundant.
Removed old debug statements
Minor tweaks to @juharris's PR: only two public methods, with RDFHandlers as varargs, per #482. Swapped order of args for symmetry.
Merge branch 'master' of github.com:tinkerpop/blueprints
Merge pull request #493 from juharris/GraphSail-addVertex

GraphSail: add vertex to the store -- Handy; I will add a getVertex, as well.
Added GraphSail#getVertex to complement GraphSail#addVertex, + unit tests
Merge branch 'master' of github.com:tinkerpop/blueprints