Added logging support using SLF4J backed by Log4J.

pit-swing/griffon-app/conf/Events.groovy

@@ -0,0 +1,5 @@
+import org.slf4j.LoggerFactory
+
+onNewInstance = { klass, type, instance ->
+    instance.metaClass.logger = LoggerFactory.getLogger(klass.name)
+}