Add formatter for service inspect

Allows the user to use `pretty` as the format string.
This enables users to put custom format options into their CLI config
just like is supported for `docker ps` and `docker images`

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

docs/reference/commandline/cli.md

@@ -143,6 +143,13 @@ Docker's client uses this property. If this property is not set, the client
 falls back to the default table format. For a list of supported formatting
 directives, see the [**Formatting** section in the `docker images` documentation](images.md)
 
+The property `serviceInspectFormat` specifies the default format for `docker
+service inspect` output. When the `--format` flag is not provided with the
+`docker service inspect` command, Docker's client uses this property. If this
+property is not set, the client falls back to the default json format. For a
+list of supported formatting directives, see the
+[**Formatting** section in the `docker service inspect` documentation](service_inspect.md)
+
 Following is a sample `config.json` file:
 
     {
@@ -151,6 +158,7 @@ Following is a sample `config.json` file:
       },
       "psFormat": "table {{.ID}}\\t{{.Image}}\\t{{.Command}}\\t{{.Labels}}",
       "imagesFormat": "table {{.ID}}\\t{{.Repository}}\\t{{.Tag}}\\t{{.CreatedAt}}",
+      "serviceInspectFormat": "pretty",
       "detachKeys": "ctrl-e,e"
     }
 

docs/reference/commandline/service_inspect.md

@@ -130,6 +130,8 @@ Ports:
  PublishedPort = 4443
 ```
 
+You can also use `--format pretty` for the same effect.
+
 
 ### Finding the number of tasks running as part of a service