Add iterator for const version of UniquePtrList.

src/Memory/UniquePtrList.hpp

@@ -12,6 +12,7 @@ namespace ArbUt {
     private:
         std::vector<ValueT*> _vector;
         using iterator = typename std::vector<ValueT*>::iterator;
+        using const_iterator = typename std::vector<ValueT*>::const_iterator;
 
     public:
         inline UniquePtrList() : _vector() {}
@@ -62,6 +63,8 @@ namespace ArbUt {
 
         iterator begin() { return _vector.begin(); }
         iterator end() { return _vector.end(); }
+        const_iterator begin() const { return _vector.begin(); }
+        const_iterator end() const { return _vector.end(); }
 
         ValueT* const* RawData() const { return _vector.data(); }