Migrate from dune-fufem to dune-functions bases

Migrate from dune-fufem to dune-functions bases.

dune/gfe/realtuple.hh

@@ -66,6 +66,17 @@ public:
         return *this;
     }
 
+    RealTuple& operator-=(const Dune::FieldVector<T,N>& other) {
+        data_ -= other;
+        return *this;
+    }
+
+    template <class T2>
+    RealTuple& operator-=(const RealTuple<T2,N>& other) {
+        data_ -= other.data_;
+        return *this;
+    }
+
     /** \brief Assigment from RealTuple with different type -- used for automatic differentiation with ADOL-C */
     template <class T2>
     RealTuple& operator <<= (const RealTuple<T2,N>& other) {
@@ -74,6 +85,11 @@ public:
         return *this;
     }
 
+    /** \brief Const random-access operator*/
+    T operator[] (const size_t indexVariable ) const {
+        return data_[indexVariable];
+    }
+
      /** \brief Rebind the RealTuple to another coordinate type */
     template<class U>
     struct rebind