Strip the line to filter lines composed of only whitespaces

Fix #9395
Allow Ansible to honor the "no_proxy" environment varaible.
Do not assume that stdin is a tty

This can be used from another non interactive software, see #9695
for details.
Use --version to see if less can be executed

(less) 2> /dev/null would fail if stdin is /dev/null.
Sinceless --version do not read anything from stdin,
it is perfect for seeing if the software exist or not.

Also replace the whole os system detection by directly
using subprocess ( as we use it elsewhere, we already
depend on it ).
Do not use the variable name as a key for the result of the module

Using the variable name can interfere with various systems
used to communicate between modules and ansible ( as
reported in #7732 , where ansible_facts is a reserved key for
updating the fact cache, for example ).
Fix for not all platforms having optional libraries at the proper versions.
Comment remote_port in the example ansible.cfg so users do not override their .ssh/config settings by default
Update core modules
Update core so docs build
Fix documentation syntax problems
Merge pull request #9805 from mscherer/fix_9395

Strip the line to filter lines composed of only whitespaces
fix vars_prompt no/false values
Merge pull request #9807 from swimlappy/noproxy

Request: Honor the "no_proxy" environment variable in Ansible
Merge pull request #9809 from mscherer/fix_9695

Make sure ansible-doc work when stdin is not a tty
Merge pull request #9810 from mscherer/fix_7732

Do not use the variable name as a key for the result of the module
Merge pull request #9830 from nathancahill/vars_prompt-no-value

Fix vars_prompt no/false default values
math filters!
removed stray j
removed redundant math functions as jinja2 provides abs() and round()
already
Merge pull request #9832 from bcoca/math_filters

math filters!