Port ansible doc for plugins to use DOCUMENTATION variables

* Using docstrings conflicts with the standard use of docstrings
* PYTHON_OPTIMIZE=2 will omit docstrings.  Using docstrings makes future
  changes to the plugin and module code subject to the requirement that we
  ensure it won't be run with optimization.

lib/ansible/plugins/connection/network_cli.py

@@ -2,8 +2,10 @@
 # (c) 2017 Ansible Project
 # GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
 
-"""
-DOCUMENTATION:
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+DOCUMENTATION = """
     author: Ansible Networking Team
     connection: network_cli
     short_description: Use network_cli to run command on network appliances
@@ -42,9 +44,6 @@ DOCUMENTATION:
         default: 120
 """
 
-from __future__ import (absolute_import, division, print_function)
-__metaclass__ = type
-
 import json
 import logging
 import re