Allow access to minimum/maximum values of NumericalPropertys

include/openspace/properties/numericalproperty.h

@@ -42,6 +42,9 @@ public:
 	bool setLua(lua_State* state) override;
 	int typeLua() const override;
 
+	T minValue() const;
+	T maxValue() const;
+
     virtual std::string className() const override;
 
     using TemplateProperty<T>::operator=;

include/openspace/properties/numericalproperty.inl

@@ -200,5 +200,15 @@ int NumericalProperty<T>::typeLua() const {
 }
 
 
+template <typename T>
+T NumericalProperty<T>::minValue() const {
+	return _minimumValue;
+}
+
+template <typename T>
+T NumericalProperty<T>::maxValue() const {
+	return _maximumValue;
+}
+
 } // namespace properties
 } // namespace openspace