Add ResolveVariables()

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

lib/variables/variable-string.cpp

@@ -50,6 +50,12 @@ void StringVariable::Save(obs_data_t *obj, const char *name) const
 	obs_data_set_string(obj, name, _value.c_str());
 }
 
+void StringVariable::ResolveVariables()
+{
+	Resolve();
+	_value = _resolvedValue;
+}
+
 const char *StringVariable::c_str()
 {
 	Resolve();