InitConfig: Internalize FILLEPS Keyword

This commit extends the InitConfig class to support querying whether
or not the FILLEPS keyword is present in the PROPS section.  Note
that we only look for the keyword in PROPS (not the whole input
deck), since the keyword is only permitted in PROPS.

Add unit tests to exercise the new ability.

opm/parser/eclipse/EclipseState/InitConfig/InitConfig.hpp

@@ -41,12 +41,18 @@ namespace Opm {
         bool hasEquil() const;
         const Equil& getEquil() const;
 
+        bool filleps() const
+        {
+            return this->m_filleps;
+        }
+
     private:
+        Equil equil;
+        bool m_filleps;
+
         bool m_restartRequested = false;
         int m_restartStep = 0;
         std::string m_restartRootName;
-
-        Equil equil;
     };
 
 } //namespace Opm