Issue302 inverse x

[mwetter]

This is ready to merge when the fixme's are addressed by @marcusfuchs in #301.

This merge contains the reimplementation of the flow functions for #301 and a bug fix for #302 .
The example Annex60.Utilities.Math.Functions.Examples.InverseXRegularized has been revised to also plot the 1st and 2nd derivative of Annex60.Utilities.Math.Functions.inverseXRegularized which has been newly implemented as the old implementation was only once continuously differentiable.

[mwetter]

@marcusfuchs
Please hold off with reviewing inverseXRegularized as I am working on a more efficient implementation.
The other changes from #301 won't be affect, hence they are ready for review.

[mwetter]

@marcusfuchs
This is ready to be merged. I merged it already to the master of the Buildings library in lbl-srg/modelica-buildings#448

Across a few large test models, the simulation time is about 5% to 10% faster.

[marcusfuchs]

@mwetter : Github warns of conflicts for this merge. Should I go ahead and resolve these conflicts or is there something wrong with the current version?

[marcusfuchs]

I now deleted FirstDerivative, SecondDerivative and FlowFunctions as suggested in #301 and fixed the merge conflicts by using the more recent versions of the 3 files.
@mwetter: If this is ok with you, I (or you again) can merge this, as from my side all changes appear to be fine.