This reverts commit f2e5bf06.

Issue #2941029 by Jon Pugh: Merge remote-tracking branch 'origin/2941029-platform-wide-settings' into 7.x-3.x

I found that when updating MySQL systemd would restart the queued 3 times 100ms apart. While updating MySQL took a bit more then 0.3 seconds.

Herman van Rink authored Jan 31, 2018 and Jon Pugh committed Jan 31, 2018

Issue #2911861 by helmo, Jon Pugh: Hosting Features submit should trigger drush cache clear after verify

Issue #2940702 by Jon Pugh: Unable to override Drupal 8 in local.settings.php: Change `include_once` to `include`. Since Drupal 8 uses `require` and not `require_once`, it's possible settings.php will be included twice. Provision should include custom settings every time.

  - Typo.

  - Cleanup docs and move to provision.api.php

  - If check for shell_exec fails, log a warning.

Merge branch '2937147-composer-install' of git.drupal.org:project/provision into 2937147-composer-install

 - Wrap the whole thing in a check for a drush option `provision_composer_install_platforms`. If set to FALSE, don't even check for composer.json.
 - Make `provision_composer_install_command` a variable, allowing customization.
 - Rename the variable `provision_composer_install_platforms`.

This reverts commit 76ff4485.