Adds new well formulation

Todo: incorporate WellDensitySegment. Currently values of the pressure
drop is hardcoded to make the rest of the code work
Todo: make it possible to shut perforation with crossflow.

opm/autodiff/FullyImplicitBlackoilSolver.hpp

@@ -158,6 +158,15 @@ namespace Opm {
         computeAccum(const SolutionState& state,
                      const int            aix  );
 
+        void
+        addOldWellEq(const SolutionState& state);
+
+        void
+        addWellControlEq(const SolutionState& state);
+
+        void
+        addWellEq(const SolutionState& state);
+
         void
         assemble(const V&             dtpv,
                  const BlackoilState& x   ,