Add ResolveVariables()

Settings will be set to fixed values based on the values of the
variables used.

lib/variables/variable-number.hpp

@@ -22,6 +22,7 @@ public:
 	Type GetType() const { return _type; }
 	bool IsFixedType() const { return _type == Type::FIXED_VALUE; }
 	std::weak_ptr<Variable> GetVariable() const { return _variable; }
+	void ResolveVariables();
 
 private:
 	Type _type = Type::FIXED_VALUE;