Discontinue VFS

Due to various design and implementation problems, especially on Windows, we should discontinue VFS. It could be replaced by the following:

• URL handlers:
  • A "deployment" URL handler which could possibly use standard !/ syntax (but extended to arbitrary levels) to identify nested JARs, like this: deployment:/myApp.ear!/lib/someThing.jar!/org/foo/Bar.class
  • An "ext" URL handler which would identify extensions by name: ext:/my-extension/org/foo/Bar.class
  • Normal jar URLs for filesystem JARs
• The URL handlers should use a "current application server" context selector in order to convert the global ref into an AS instance-relative ref, as we should not be maintaining global state
• Separate module loaders (and services, if appropriate) for the above three cases, whose class loaders in turn use the above URL schemes (as appropriate) for code source and resource URLs