zipfs and write support

[Joel Uckelman]

Thus spake Alan Bateman:
>    
> It sounds like you've made good progress. If it extends the existing zip 
> provider then I assume it must still be based on java.util.zip, right? 
> Have you given any thought to access from others VM or applications? 
> It's hard to comment on the locking without more information - if there 
> a file opened for writing then does it block all other (read) access to 
> the "file system"?
> 
> -Alan.

It dawned on me just now that subtree locking isn't necessary for handling
nonoverlapping writes here, because you can neither delete nor move nonempty
directories with the Path API---anything whch can be written to is a leaf.
Per-Path locking will be easy to do, I might even finish it this evening.

-- 
J.