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/strategy/linear.py

@@ -14,8 +14,11 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
-'''
-DOCUMENTATION:
+# Make coding more python3-ish
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+DOCUMENTATION = '''
     strategy: linear
     short_description: Executes tasks in a linear fashion
     description:
@@ -27,9 +30,6 @@ DOCUMENTATION:
      - This was the default Ansible behaviour before 'strategy plugins' were introduced in 2.0.
     author: Ansible Core Team
 '''
-# Make coding more python3-ish
-from __future__ import (absolute_import, division, print_function)
-__metaclass__ = type
 
 from ansible.errors import AnsibleError
 from ansible.executor.play_iterator import PlayIterator