Standardize API keys: CamelCase

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
update docs

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Adding User Guide

* Added User Guide section outlines.
* Added User Guide to menu.
* Moved HTTPS example to articles.
* Replaced Hello World example with User Guide.
* Moved use cases out of examples.
* Updated Introduction to add User Guide.
* Redirected migrated /use and /articles links.
* Added Docker.io section
* Added Dockerized section
* Added Using Docker section
* Added Docker Images section
* Added Docker Links section
* Added Docker Volumes section

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)
pkg: mflag: flag: make mflag strip quotes in -flag="var" forms

This patch improves the mflag package to ensure that things arguments
to mflag such as `-flag="var"` or `-flag='var'` have the quotes
stripped from the value (to mirror the getopt functionality for similar
flags).

Docker-DCO-1.1-Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> (github: cyphar)
pkg: mflag: flag: added tests for quote-stripped flags

This patch adds some tests to ensure that quoted flags are properly
handled by the mflag package.

Docker-DCO-1.1-Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> (github: cyphar)
Adding "stats" and "spec" option to nsinit binary which will print the stats and spec respectively.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
Merge pull request #6154 from SvenDowideit/pr_out_adding_user_guide

Adding User Guide
Update networking.md

grammar

Docker-DCO-1.1-Signed-off-by: Andre Dublin <81dublin@gmail.com> (github: andredublin)

rebased by

Docker-DCO-1.1-Signed-off-by: SvenDowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
Remove unused and racy "used" param from streamformatter

Also tests written
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Merge pull request #6157 from SvenDowideit/pr_out_update_networking_md

Update networking.md
Merge pull request #6116 from vishh/nsinit_stats

Adding "stats" and "spec" option to nsinit CLI
Update cpu stat test for no error
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #6150 from LK4D4/remove_used_from_streamformatter

Remove unused and racy "used" param from streamformatter
Merge pull request #6130 from vieux/standardize_api_keys

Standardize api keys to CamelCase
Merge pull request #6147 from cyphar/6142-mflag-strip-quotes-long-equal-form

mflag: strip quotes in certain forms from flag values
Merge pull request #6160 from crosbymichael/update-test-for-nil-error

Update cpu stat test for no error