oracle - fixed first and added more tests

Fixed the first(...) method and added several checks to the integration tests of the oracle dialect.

I also had to add an orderBy() to some tests because the resulting order is not deterministic, Oracle does not sort implicitly (or by accident) by the id.

It's now also possible to avoid direct comparison of arrays/object in the tester by providing a function (that should return true if ok) instead. See avg() test for example.