Add more file/directory primitives.

[skx]

#47 covers a reworking of file/directory handling.

In addition to the work described there we should add:

• file.stat()
  • As mentioned.
• unlink
  • Delete a file/directory.
• mkdir
  • Make a directory.
  • mkdir( "/tmp/foo/bar", { "mode": "0755" } )

[skx]

I guess I forgot:

• chown
• chgrp
• chmod

[skx]

Ignored chgrp + chmod specifically because they require a Unix-system, and there are choices to be made:

 chmod( "/tmp/blah", "root") 

vs:

 chmod( "/tmp/blah", 0) 

The former is kinda OK, but the latter means we have to allow lookup of passwd-entries, to make the mapping from skx -> 1003, root -> 0, etc.