Add triples only if they are not stoppped at

* update tests

`GraphExtract` should updates its model _after_ it is checked if the triple should be taken into account or stopped at (ok, it's maybe not really a bug , depending on your your definition if "stop at" is meant inclusive or exclusive).

As reflected in the test, this prohibits the addition of a triple like `s p _o` using `TripleBoundary.stopAtAnonObject`. If you want to include this triple you would now use `TripleBoundary.stopAtAnonSubject`.

*I admit that this may break applications and thus is not a good idea.*
It breaks down to my following question:
How could a `TripleBoundary` looks like if you only want triples with one given subject?
(with the changes reflected in this pull request #4, one can do something like this https://github.com/lobid/lodmill/blob/9a87ba36f7efd775dae1f61bb21f45031fa27468/lodmill-rd/src/main/java/org/lobid/lodmill/SubjectBoundary.java )