`write_back` parameter in `getResult`. While the previous
version worked in the sense, that it allowed to `save` computations
already done, I disliked the state-changing behaviour of that
implemetation. Now we have a way to realize the registered
test functions into a new `SaQC` without modifying the old one and
don't violate the functional interface of the `SaQC`-Objects
any more.