INSERT containing GRAPH with variable for name

Constructs like
INSERT { GRAPH ?g { ... } } and
DELETE { GRAPH ?g { ... } }
are now handled correctly: The value of the variable ?g is used as the
name of the graph. Before, the variable ?g itself was used.
initNs and initBindings for processUpdate and prepareQuery
Merge pull request #11 from uholzer/init-ns-and-bindings

initNs and initBindings for processUpdate and prepareQuery
Merge pull request #10 from uholzer/bug-update-vargraph

INSERT containing GRAPH with variable for name