Added test for optional attribute in Action

SDT/schema4.0/test/action-test.xml

+<?xml version="1.0" encoding="iso-8859-1"?>
+<!-- Test the data types references -->
+
+<Domain id="action-test" xmlns="http://homegatewayinitiative.org/xml/dal/4.0" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+	<ModuleClasses>
+		<ModuleClass name="TestActions">
+			<Actions>
+				<Action name="testActionOptional" optional="true">
+				</Action>
+			</Actions>
+		</ModuleClass>
+	</ModuleClasses>
+
+</Domain>
\ No newline at end of file