`OffspecSimulation` contains and uses members `OffspecDetector` and `IBeamScan` and each of them has its own analyzer. Now `IBeamScan::analyzerMatrix()` is used for computation in `OffspecSimulation::runComputation`. For reasons of consistency, we should use `OffspecDetector::analyzer().matrix()` instead. Moreover, `IBeamScan::analyzerMatrix()` should be hidden (only for offspec) from users to prevent ambiguity.