#14 support thinlet (XUL) in describing menus

[Ray Case]

Any chance you can externalize the presentation layer
of systray4j into thinlet or XUL format so that users can
skin the menu by an external file. This would make this
project even more awesome. I chose to stay with
systray4j and thinlet than migrating SWT. Being able to
alter the appearance of systray4j's menu through XUL
would be tremendous!!!

Thanks!
Ray