initial vfs work

Well, here is the initial vfs work. All tests in o1, other, browser (I have a normal amount of failures) and sanity pass.

I'd like input on the VFS namespace. I set that up during dev just to kind of split up private internal filesystem functionality (FS) and the external public functionality (VFS). However, it's kind of odd for users to use it instead of the FS namespace. I guess I could move all of the VFS code into the FS namespace and prefix the current FS members with _ or something. It's a bit weird to design due to the implicit eval of library files, I can't actually make those functions private.

I'd eventually like to:
 * remove the USE_OLD_FS setting
 * split off FS / VFS namespaces into library_fs.js
 * removed createLazyFile

However, I guess all of these tasks should happen after this branch makes it into incoming.

Also, there is still documentation to write, but I'm not sure that blocks this due to the compatibility layer.