Added test for ‘default’ attribute in DataPoint.

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

+<?xml version="1.0" encoding="iso-8859-1"?>
+<!-- Test the EnumType -->
+
+<Domain id="datapoint-test" xmlns="http://homegatewayinitiative.org/xml/dal/4.0" xmlns:xi="http://www.w3.org/2001/XInclude">
+	<ModuleClasses>
+		<ModuleClass name="TestDataPoint">
+			<Data>
+				<DataPoint name="TestDataPoint" optional="true" default="foo">
+					<DataType>
+						<SimpleType type="string" />
+					</DataType>
+				</DataPoint>
+			</Data>
+		</ModuleClass>
+	</ModuleClasses>
+</Domain>
\ No newline at end of file