Make the wellModel self-contained

The wellModel is now persistent over the time steps,
with an update method called every reportStep/episode.

This allows the following simplifications:

    1. move the wellState to the WellModel
    2. add a ref to the ebosSimulator to the wellModel
    3. clean up the parameters passed to the wellModel methods
    4. move RESV handling to the WellModel and the rateConverter
    5. move the econLimit update to the WellModel

opm/autodiff/MultisegmentWell.hpp

@@ -47,6 +47,9 @@ namespace Opm
 
         using Base::has_solvent;
         using Base::has_polymer;
+        using Base::Water;
+        using Base::Oil;
+        using Base::Gas;
 
         // TODO: for now, not considering the polymer, solvent and so on to simplify the development process.