Add `capability` filter to `docker plugin ls`

This fix adds `--filter capability=[volumedriver|authz]` to `docker plugin ls`.

The related docs has been updated.

An integration test has been added.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

docs/extend/config.md

@@ -51,9 +51,13 @@ Config provides the base accessible fields for working with V0 plugin format
 
       currently supported:
 
-      	- **docker.volumedriver/1.0**
+        - **docker.volumedriver/1.0**
 
-      	- **docker.authz/1.0**
+        - **docker.networkdriver/1.0**
+
+        - **docker.ipamdriver/1.0**
+
+        - **docker.authz/1.0**
 
     - **`socket`** *string*
 

docs/reference/commandline/plugin_ls.md

@@ -53,11 +53,26 @@ than one filter, then pass multiple flags (e.g., `--filter "foo=bar" --filter "b
 The currently supported filters are:
 
 * enabled (boolean - true or false, 0 or 1)
+* capability (string - currently `volumedriver`, `networkdriver`, `ipamdriver`, or `authz`)
 
 ### enabled
 
 The `enabled` filter matches on plugins enabled or disabled.
 
+### capability
+
+The `capability` filter matches on plugin capabilities. One plugin
+might have multiple capabilities. Currently `volumedriver`, `networkdriver`,
+`ipamdriver`, and `authz` are supported capabilities.
+
+```bash
+$ docker plugin install --disable tiborvass/no-remove
+tiborvass/no-remove
+
+$ docker plugin ls --filter enabled=true
+NAME                  TAG                 DESCRIPTION                ENABLED
+```
+
 
 ## Formatting