heavyoil sagd_cyclic shows unphysical behaviour

@holle discovered today that the sagd_cyclic and also the sagd_cyclic_hyst show some presumably unphysical behaviour. This should be a comparison between dumux releases/2.12 and dumux-lecture on releases/2.12 with dumux releases/3.0 and dumux-lecture with releases/3.0. We want to use the 3.0 version and regard the 2.12 as a reference.

I already found some obvious things that were missing so that the exercise actually runs and uses the CheckPointTimeLoop and started fixing this on !74 (closed).

The general problem however still seems to be that there is maybe (needs to be checked)"too much injection" and that when the injection is stopped the gas phase saturation does not decrease (as on 2.12) but continues increasing for some time even though the injection (and therefor pressure) are stopped

Our guideline would be:

• run the standard sagd on 2.12 and compare with 3.0 -> are they the same? Hopefully yes.
• test sagd_cyclic and sagd_cyclic_hyst

Possible things to investigate

• is injection the same (hopefully verified with sagd-problem)
• changes in the privar-switch (problem occurs when gas phase disappears)
• changes to the fluidsystem/components (molarDensity?)
• changes to constraintsolver/matrix-preconditioning
• extension of IAPWS region 2 (minimal change)