Comment how to make a signing certificate.

core/maven.xml

@@ -28,6 +28,7 @@
     <postGoal name="jar:jar">
         <j:if test="${context.getVariable('signature.alias') != null}">
         	<echo>signature.alias defined; signing JAR(s)...</echo>
+			<!-- To create your own free signing certificate, see http://www.dallaway.com/acad/webstart/  -->
 			<ant:signjar lazy="true" alias="${signature.alias}" storepass="${signature.storepass}" keystore="${signature.keystore}">
 				<fileset dir="${maven.build.dir}">
 					<include name="*.jar"/>