show a progress bar while the core loads

gui/griffon-app/controllers/com/muwire/gui/MainFrameController.groovy

@@ -0,0 +1,18 @@
+package com.muwire.gui
+
+import griffon.core.artifact.GriffonController
+import griffon.core.controller.ControllerAction
+import griffon.inject.MVCMember
+import griffon.metadata.ArtifactProviderFor
+import javax.annotation.Nonnull
+
+@ArtifactProviderFor(GriffonController)
+class MainFrameController {
+    @MVCMember @Nonnull
+    MainFrameModel model
+
+    @ControllerAction
+    void click() {
+        model.clickCount++
+    }
+}