Add a parent man page for docker volumes command

It is difficult to gather information about docker volumes command
without a parent man page.

This man page attempts to explain docker volumes and then references
the command man pages.

Signed-off-by: Dan Walsh <dwalsh@redhat.com>

man/docker-volume.1.md

@@ -0,0 +1,62 @@
+% DOCKER(1) Docker User Manuals
+% Docker Community
+% Feb 2016
+# NAME
+docker-volume - Create a new volume
+
+# SYNOPSIS
+**docker volume** [OPTIONS] COMMAND
+[**--help**]
+
+# DESCRIPTION
+
+docker volume command manages content volumes for docker containers.
+
+## Data volumes
+
+A *data volume* is a specially-designated directory within one or more
+containers.
+
+Data volumes provide several useful features for persistent or shared data:
+
+Volumes are initialized when a container is created. If the container's
+base image contains data at the specified mount point, that existing data is
+copied into the new volume upon volume initialization. (Note that this does
+not apply when [mounting a host directory](#mount-a-host-directory-as-a-data-volume).)
+
+Data volumes can be shared and reused among containers.
+
+Changes to a data volume are made directly.
+
+Changes to a data volume will not be included when you update an image.
+
+Data volumes persist even if the container itself is deleted.
+
+Data volumes are designed to persist data, independent of the container's life
+cycle. Docker therefore *never* automatically deletes volumes when you remove
+a container, nor will it "garbage collect" volumes that are no longer
+referenced by a container.
+
+# OPTIONS
+**--help**
+  Print usage statement
+
+# COMMANDS
+**create**
+  Create a volume
+  See **docker-volume-create(1)** for full documentation on the **create** command.
+
+**inspect**
+  Return low-level information on a volume
+  See **docker-volume-inspect(1)** for full documentation on the **inspect** command.
+
+**ls**
+  List volumes
+  See **docker-volume-ls(1)** for full documentation on the **ls** command.
+
+**rm**
+  Remove a volume
+  See **docker-volume-rm(1)** for full documentation on the **rm** command.
+
+# HISTORY
+Feb 2016, created by Dan Walsh <dwalsh@redhat.com>