Re-added B-spline transformation for non-linear RT alignment in MapAlignerIdentification

Including updated tests.
This doesn't help in my view as it just artificially introduces a common interface. Interpretation of the stuff you get back from the param object requires stronger semantic coupling as it is not checked at compile time. This is especially bad for low or medium level functioniallity. To put this different: I think it is not a good idea to try to move in the direction of a general fitter base class because there are just too many exeptions. Even if there was one, benefits would be neglectable and the price: 1. awful slow queries and 2. semantic run time coupling  are much too high in my view.