Add ArcSinH transformation as parametrized in Gating-ML 2.0

Hi guys,
just a few mostly trivial additions to add the ArcSinH transformation the way it is parameterized in Gating-ML 2.0 so that I can use it when parsing Gating-ML 2.0 from flowUtils. 

I was also considering whether to keep working on some more Gating-ML 2.0 transformations first, but came to a conclusion that smaller pull requests are likely better and easier to review.

Cheers,
Josef