libcontainer: remove LinuxFactory

Since LinuxFactory has become the means to specify containers state
top directory (aka --root), and is only used by two methods (Create
and Load), it is easier to pass root to them directly.

Modify all the users and the docs accordingly.

While at it, fix Create and Load docs (those that were originally moved
from the Factory interface docs).

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

list.go

@@ -121,11 +121,6 @@ func getContainers(context *cli.Context) ([]containerState, error) {
 		// Report other errors, including non-existent custom --root.
 		return nil, err
 	}
-	factory, err := libcontainer.New(root)
-	if err != nil {
-		return nil, err
-	}
-
 	var s []containerState
 	for _, item := range list {
 		if !item.IsDir() {
@@ -146,7 +141,7 @@ func getContainers(context *cli.Context) ([]containerState, error) {
 			owner.Name = fmt.Sprintf("#%d", uid)
 		}
 
-		container, err := factory.Load(item.Name())
+		container, err := libcontainer.Load(root, item.Name())
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "load container %s: %v\n", item.Name(), err)
 			continue