removing well_soltutions_ from WellStateFullyImplicitBlackoilDense

adding function setWellSolutions() to StandardWell.

The class WellStateFullyImplicitBlackoilDense is ready to be removed
now, while the only thing can go wrong compred with the original version
is the group control, which is not tested yet.

opm/autodiff/StandardWellsDense.hpp

@@ -172,7 +172,7 @@ namespace Opm {
             /// return true if wells are available on this process
             bool localWellsActive() const;
 
-            void setWellVariables(const WellState& xw);
+            void setWellVariables();
 
             void computeAccumWells();