fixes to config/setting retrieval

- better variable precedence management
- universal plugin option handling
- also updated comments for future directions
- leverage fragments for plugins
- removed fact namespacing
- added 'firendly name' field
- updated missing descriptions
- removed some unused yaml entries, updated others to reflect possible future
- documented more plugins
- allow reading docs using alias
- short licenses
- corrected args for 'all plugins'
- fixed -a option for ansible-doc
- updated vars plugins to allow docs
- fixed 'gathering'
- only set options IF connection
- added path list and renamed pathspec mostly the diff is , vs : as separator
- readded removed config entries that were deprecated but had no message ... and deprecated again
- now deprecated entries give warning when set

lib/ansible/plugins/vars/host_group_vars.py

@@ -27,6 +27,18 @@ DOCUMENTATION:
         - Only applies to inventory sources that are existing paths.
     notes:
         - It takes the place of the previously hardcoded group_vars/host_vars loading.
+    options:
+      _valid_extensions:
+        default: [".yml", ".yaml", ".json"]
+        description:
+          - "Check all of these extensions when looking for 'variable' files which should be YAML or JSON or vaulted versions of these."
+          - 'This affects vars_files, include_vars, inventory and vars plugins among others.'
+        env:
+          - name: ANSIBLE_YAML_FILENAME_EXT
+        ini:
+          - section: yaml_valid_extensions
+            key: defaults
+        type: list
 '''
 
 from __future__ import (absolute_import, division, print_function)