Enable documentation in plugins

Made ansible-doc more plugin agnostic
We can have docs in lookup, callback, connectionm strategy, etc
Use first docstring and make pepizis happy
generalized module_docs to plugin_docs
documented cartesian, ssh, default, jsonfile, etc as examples
changed lack of docs to warning when listing
made smarter about bad docstrings
better blacklisting
added handling of options/config/envs/etc
move blacklist to find_plugins, only need once

lib/ansible/plugins/lookup/etcd.py

@@ -14,6 +14,43 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+'''
+DOCUMENTATION:
+    author:
+        - Jan-Piet Mens (@jpmens)
+    lookup: etcd
+    version_added: "2.1"
+    short_description: get info from etcd server
+    description:
+        - Retrieves data from an etcd server
+    options:
+        _raw:
+            description:
+                - the list of keys to lookup on the etcd server
+            type: string
+            required: True
+        _etcd_url:
+            description:
+                - Environment variable with the url for the etcd server
+            default: 'http://127.0.0.1:4001'
+            env_vars:
+                - ANSIBLE_ETCD_URL
+        _etcd_version:
+            description:
+                - Environment variable with the etcd protocol version
+            default: 'v1'
+            env_vars:
+                - ANSIBLE_ETCD_VERSION
+EXAMPLES:
+    - name: "a value from a locally running etcd"
+      debug: msg={{ lookup('etcd', 'foo') }}
+RETURN:
+    _list:
+        description:
+            - list of values associated with input keys
+        type: strings
+'''
+
 from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type