Fix various inventory scripts to use env python

Fix https://github.com/ansible/ansible/issues/9948

fixed bad exampel for library that was library_path

not work

Enable environment keyword at play level

Fix some typos in developing_modules.rst

Improve wording in playbooks_intro.rst

I was reading the docs and thought "that wording seems off."

facts caching: fix missing json in jsonfile caching

Need for clarification brought up here:
https://github.com/ansible/ansible/issues/9877

test_git: add tests for `refspec' argument

Fix conditionals doc example

There are still a couple of modules that use their own lists, but that should not prevent this merge, those should be adapted to use this list in subsequent patch

cache json fixes

Use most recent parameters for yum

now uses utils.jsonify which does proper utf8 encoding

Add a explicit error when fact_caching_connection is not set

Add a new inventory group so you can see instances in a particular VPC

By default, jsonfile is not documented, and the error message
when fact_caching_connection is not set is a bit puzzling, so
a error message would be beeter ( documentation too ). While redis
is faster for bigger setup, jsonfile is fine for a small setup
and is easier to deploy.

The module will then stop ansible-playbook, as this match better
the philosophy of Ansible being a fail-fast system.

Includes a basic test of the clone and update cases.

math filters!