Not wicket, but they're typically used by most java apps. They're complementary to spring.
So you can put .java and .html and .properties related files in the same folder, not scattered
You can see my progress on this in my own fork https://github.com/ceefour/spring-entry I'll make pull request when done.
Yeah that's a cool project :) I don't know detail how @MarcGiffing set up his project but knowing spring boot and wicket, there's no worry.