Fixes for dev mode code-and-refresh netbeans compatibility

It turns out we don't need src/main/java on the resource path at all. Simply removing it (and the gwt:resources execution) causes Maven and Eclipse to behave more like NetBeans (that is, they no longer copy static resources to WEB-INF/classes during the build). Without those copied .java and .html files in the way, dev mode should work equally well for you in netbeans now!