Make PatternTrackParameters a subclass of ParametersBase

This merge request makes the PatternTrackParameters class a subclass of ParametersBase. This is achieved by progressively altering data members and methods to match those of ParametersBase and finally unifying the two types in a single class hierarchy. The advantage of this is that it will allow us to operate on PatternTrackParameters through methods taking ParametersBase arguments through subtype polymorphism.

These changes should be invariant in terms of physics and CPU performance.