Update headings plus edits for consistency and clarity in Config Reference

Partial-Bug: #1250515

author: diane fleming

Change-Id: I92c9ad25ee5bbd2c9334c4860637faa1b358718b
backport: havana
Fixed wording and reorganised Block Storage intro

As per the bug, updated the wording and slightly reorganised
the Block Storage intro. Watch this space for the rest of the book.

Change-Id: I38d1a6c0c9dc093235db0573399fab459a5bc1db
backport: havana
Partial-Bug: #1251195
Quantum is replaced by Neutron in Openstack Training Guides.

Change-Id: Ia147d362c3eeae68a7924619ecb3c2b0e98112d7
Closes-Bug: #1250538
Editorial updates to common files, including sentence-style headings and consistency/clarity edits

Partial-Bug: #1250515

backport: havana

Change-Id: I9675dffd130c8aa6343143d9806adb4e0b74a55d
author: diane fleming
Merge "Fixed wording and reorganised Block Storage intro"
Merge "Update headings plus edits for consistency and clarity in Config Reference"
Merge "Editorial updates to common files, including sentence-style headings and consistency/clarity edits"
Merge "Quantum is replaced by Neutron in Openstack Training Guides."