Testing: Update PHPUnit versions

Adding theming information

UI: fix font-awesome icon links to show v4.7

update intro text

update re Jira deprecation

Update hook_civicrm_emailProcessorContact.md

Formatting and wording

Restructure to better incorporate Symfony hooks

Cmtool usage updates

Minor tweaks on recommendations

Correct URL for Extension Review Request

JIRA is dead.

Actually I think we should put the 'other platforms' first & the more specific options at the end though

Buildkit: update php, nodejs, mysql versions

Add in Change log describing the changes made to API for dev/core#475

Moved Jira to "out of use" as it's now been archived.