Implement --device idType://id for ctr run on Windows

Also fixes the issue that `ctr run` on Windows offered help for the
non-Windows implementation, but was silently ignored.

Signed-off-by: Paul "TBBle" Hampson <Paul.Hampson@Pobox.com>

cmd/ctr/commands/commands.go

@@ -165,10 +165,6 @@ var (
 			Name:  "memory-limit",
 			Usage: "memory limit (in bytes) for the container",
 		},
-		cli.StringSliceFlag{
-			Name:  "device",
-			Usage: "file path to a device to add to the container; or a path to a directory tree of devices to add to the container",
-		},
 		cli.StringSliceFlag{
 			Name:  "cap-add",
 			Usage: "add Linux capabilities (Set capabilities with 'CAP_' prefix)",