[VariableBox] Added sequences to the variable box

It is now possible to call the value of a defined sequence anywhere.

Change-Id: I1990e93c50f9add175b7ea274e07004ba63289e5

apps/math_variable_box_empty_controller.h

@@ -13,7 +13,8 @@ public:
   enum class Type {
     None = 0,
     Expressions = 1,
-    Functions = 2
+    Functions = 2,
+    Sequence = 3
   };
   void setType(Type type);
   // View Controller