Directory layout for doing widgetset development?

I’m trying to modify an existing widgetset (specifically Peter’s MultiButton) so that I can understand how to create new widgets that I’ll need for my project.

In the Book of Vaadin, section 10.8.5 on doing GWT Development, there’s a great diagram showing an annotated project contents. Is there something similar for the
output (deployment)
directory? I’m having a lot of trouble figuring out where certain files should go. I’m using IntelliJ IDEA, so I don’t have a plug-in that will help me, and I need to understand what files go where so I can troubleshoot the problems I’m running into, e.g, “Widgetset does not contain implementation for org.vaadin.peter.multibutton.MultiButton.”

What I know so far is that there will be three main directories. Here’s the layout I have so far:

|> META-INF (only contains the MANIFEST.MF)
   \--> themes
      \--> reindeer (additions to the reindeer theme go here?)
      \--> mytheme (my own theme goes here?)
   \--> widgetsets
      \--> org.vaadin.peter.multibutton.MultibuttonWidgetset (a bunch of .cache.png and .cache.html files, along with the org.vaadin.peter.multibutton.MultibuttonWidgetset.nocache.js, clear.cache.gif, and hosted.html files)
         \--> ie6pngfix
         \--> multibutton-widget (empty, other than the img subdirectory)
            \--> img (contains a single img: arrow.png)
      \--> WEB-INF (yes, this is under widgetsets -- should this be here?)
         \--> deploy (contains two directories: rpcPolicyManifest and symbolMaps)
   |--> classes
   |    |--> org
   |    |    |--> vaadin
   |    |    |   |--> peter
   |--> lib