Make FlowNet work with pyscal 0.6.x, and add possibility of using pyscal's SCALrecommendation

[olelod]

In pyscal 0.6.x the krowend/krogend parameters are deprecated. Only kroend should be used now (both kro(swl) and kro(sgcr) should equal kroend).

pyscal also has the possibility of taking three sets of parameter values as input (low/base/high), and making SWOF/SGOF tables that are interpolated between the low/base/high inputs. This would potentially reduce the number of parameters passed on to ERT for history matching a lot.

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Contributor checklist

• 🎉 This PR closes Running the Norne case with pyscal 0.6.0 results in a warning + numerical issues #166 and closes Interpolation between low/base/high cases in pyscal #195 .
• 📜 I have broken down my PR into the following tasks:
  • Remove deprecated parameters krowend/krogend from config_file. Adding kroend.
  • Adding possibility of defining a base value for the relperm parameter, and use the SCALreccomendation functionality in pyscal to interpolate between the sets of curves
• 🤖 I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR.
• 📖 I have considered adding a new entry in CHANGELOG.md.
• 📚 I have considered updating the documentation.

[wouterjdb]

Looks good - some minor things only.

[wouterjdb]

LGTM 🚀

There are some missing descriptions in the config parser setup, but that was already the case and outside of the scope of this PR. I've made an issue on this #204.