Panos/doc fragment (#37696)

* Create PanOS module documentation fragment

- Module documentation fragment currently holds 3 parameters
- It most likely won't be used in every single module since there is
some variance

* Modified PanOS module for use doc_frags

- Where documentation is consistent, module documentation now uses a
documentation fragment instead of all documentation being contained in
the module.

* Formatting and syntax error fixes

Updated some formatting errors to make ansibot happy.

* Revisions for grammar

lib/ansible/modules/network/panos/panos_sag.py

@@ -32,18 +32,6 @@ requirements:
     - pandevice can be obtained from PyPi U(https://pypi.python.org/pypi/pandevice)
     - xmltodict can be obtained from PyPi U(https://pypi.python.org/pypi/xmltodict)
 options:
-    ip_address:
-        description:
-            - IP address (or hostname) of PAN-OS device
-        required: true
-    password:
-        description:
-            - password for authentication
-        required: true
-    username:
-        description:
-            - username for authentication
-        default: "admin"
     api_key:
         description:
             - API key that can be used instead of I(username)/I(password) credentials.
@@ -74,6 +62,7 @@ options:
         description:
             - The operation to perform Supported values are I(add)/I(list)/I(delete).
         required: true
+extends_documentation_fragment: panos
 '''
 
 EXAMPLES = '''