vfuse: add Mkdir

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
Add Rename support to fuse.

Basic testing for source/dest existing and not existing, golang behavior
differs from POSIX eg os.Rename does not cause EEXIST if target exists.

Fixes bradfitz/docker#12

Docker-DCO-1.1-Signed-off-by: Paul Nasrat <pnasrat@gmail.com> (github: pnasrat)
Merge branch 'fuse' of github.com:proppy/docker into fuse

Conflicts:
	vfuse/all_test.go
Merge branch 'fuse-rename' of github.com:pnasrat/docker into fuse

Conflicts:
	vfuse/all_test.go
	vfuse/client/client.go
	vfuse/vfused/server.go
Open, Read, and Close. For read-only so far.
Sort functions within files to minimize future merge conflicts.

Please keep sorted.
vfuse: add Rmdir

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
Merge pull request #23 from proppy/fuse

Add Rmdir
Implement Utimens

Fixes bradfitz/docker#7
Also changed nsec in Time type for int64 - it is easier to work with it.
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)