- Fix vaadin-maven-plugin bug : When packaging is JAR instead of WAR,
Vaadin create widgetsets but copy default widgetsets
(com.vaadin.DefaultWidgetSet) instead of our own widgetsets
(org.teknux.jb.examples.vaadin.AppWidgetSet)

Workaround : Add maven-resources-plugin to copy widgetsets generated
(${basedir}/src/main/webapp/VAADIN/widgetsets) to JAR
(>${project.build.directory}/classes/VAADIN/widgetsets)