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/ssh.py

@@ -4,8 +4,10 @@
 # Copyright (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 = '''
     connection: ssh
     short_description: connect via ssh client binary
     description:
@@ -169,9 +171,6 @@ DOCUMENTATION:
         - {key: scp_if_ssh, section: ssh_connection}
 '''
 
-from __future__ import (absolute_import, division, print_function)
-__metaclass__ = type
-
 import errno
 import fcntl
 import hashlib