Retire Debug Bar in favor of Query Monitor

In my testing, turning off Debug Bar lowers page load times
in wp-admin from ~7.5s to ~2.5s. We're using Query Monitor
now anyway, which provides most of the information in Debug Bar.

See #328
Grab $blog_id from get_current_blog_id() if null
Merge pull request #338 from xwp/feature/fix_wpcom_vip_quickstart_fix_domain

Fix wpcom_vip_quickstart_fix_domain to provide value for null $blog_id
Force Github plugins to update

It doesn't really matter if there's already a repo present,
we want to update the github plugins to whatever is the
latest on Github.

Fixes #278
Fix undefined batcache variable during phpunit execution
Restore wptests MySQL user password to wptests per wp-tests-config.php
Merge pull request #340 from xwp/feature/wptests-user-password

Restore wptests MySQL user password to wptests per wp-tests-config.php
Merge pull request #339 from xwp/feature/phpunit-batcache-undefined-var

Fix undefined batcache variable during phpunit execution
Merge remote-tracking branch 'upstream/master'