Improvement of CPU allocation explanation

Update of Overcommit section in order to explain clearly how CPU
allocation is done. A simple formula has been added.

Change-Id: Ieb8be5bace3c61cb43d35d9914198f8bc3fb6cb0
backport: none
Closes-Bug: #1263601
O'Reilly Edit: Database Cluster Clarification

Clarifies statement about db clustering recommendation.

Change-Id: I4cbbbd62dad1e4311d14b8667d47a91d6bfe1685
Enhance .gitignore

Add files needed for openstack-doc-tools, enhance
editor section, add comments.

Change-Id: I083670eebdf9396e8a811b54ef6b1afc5f6c42f0
Merge "O'Reilly Edit: Database Cluster Clarification"
Enable for gating with openstack-doc-tools

Add files to allow us gating via:
tox -e checkbuild
tox -e checkniceness
etc

Change-Id: I7b1754c94ebecf41683576a41b643bbe124b3b3e
Merge "Improvement of CPU allocation explanation"
O'Reilly Edit: Dashboard Clarification

This commit clarifies the role of the dashboard.

Change-Id: I48eac57f362ad176a23d371ae26c627f88d5b1ec
O'Reilly Edit: Intro sentence for hw table

This commit adds an into sentence for the hw considerations table.

Change-Id: I9508b5332f689d6e213c9986345d5ffa8951ad12
Merge "Enable for gating with openstack-doc-tools"
Allow passing arguments to tox

Pass extra arguments to tests.

This allows to run for example:
       tox -- --force

Also reorder elements of envlist.

Change-Id: I8595db1fb9ce685c85f76b94714b270ea34c9d7d
Merge "O'Reilly Edit: Intro sentence for hw table"
Merge "O'Reilly Edit: Dashboard Clarification"
Update Keyring Support

This commit updates the status of the Keyring Support feature.

Change-Id: Id7e43850af31c0978ae7658c9c2ced2f625fc137
Swap Chapters 3 and 4

It makes more sense to talk about both Cloud Controllers and Compute
Nodes prior to Scaling.

Change-Id: I08d3aad1e13bdeceb013291b5fd9a1f439e7b8ae
Clarifies when to use hyper-threading

Change-Id: I5f46e7a02a5e6c675a6c11c1126a34a563954b2e
O'Reilly Edit: Controller Node Clarification

This commit resolves the editor's comment regarding a "controller node"

Change-Id: Ib02def2fbafb4c71e248ddb0191c6a2e88cf2ae9
Merge "Allow passing arguments to tox"
Merge "Update Keyring Support"
Merge "Swap Chapters 3 and 4"
Merge "Clarifies when to use hyper-threading"