Document httpapi and cliconf plugins (#49503)

* Create new documentation pages for httpapi and cliconf

* Add new documentation to plugins toctree and Makefile

* Add DOCUMENTATION to cliconf

* Apply suggestions from code review

lib/ansible/plugins/cliconf/enos.py

@@ -16,6 +16,16 @@
 from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
+DOCUMENTATION = """
+---
+cliconf: enos
+short_description: Use enos cliconf to run command on Lenovo ENOS platform
+description:
+  - This enos plugin provides low level abstraction apis for
+    sending and receiving CLI commands from Lenovo ENOS network devices.
+version_added: "2.5"
+"""
+
 import re
 import json