dirtyvalue: Move to src/utility

src/displayapp/screens/Screen.h

@@ -9,41 +9,6 @@ namespace Pinetime {
     class DisplayApp;
 
     namespace Screens {
-
-      template <class T>
-      class DirtyValue {
-      public:
-        DirtyValue() = default; // Use NSDMI
-
-        explicit DirtyValue(T const& v) : value {v} {
-        } // Use MIL and const-lvalue-ref
-
-        bool IsUpdated() {
-          if (this->isUpdated) {
-            this->isUpdated = false;
-            return true;
-          }
-          return false;
-        }
-
-        T const& Get() {
-          this->isUpdated = false;
-          return value;
-        } // never expose a non-const lvalue-ref
-
-        DirtyValue& operator=(const T& other) {
-          if (this->value != other) {
-            this->value = other;
-            this->isUpdated = true;
-          }
-          return *this;
-        }
-
-      private:
-        T value {};            // NSDMI - default initialise type
-        bool isUpdated {true}; // NSDMI - use brace initialisation
-      };
-
       class Screen {
       private:
         virtual void Refresh() {