Dont hardcode drush site-install options in drupal:install command

[jameswilson]

We should remove the hardcoded options in the drupal:install command, so that each project can define the options they need inside their own repository's /drush/drushrc.php file (for drush 8+).

The following snippet is what we're using on a D8 project:

// Use a predetermined username and email and install Drupal using the project's exported config.
$command_specific['site-install'] = [
  'minimal',
  'config-dir' => '../config/sync',
  'account-name' => 'myhardtoguessadminaccountusername',
  'account-mail' => '[email protected]',
];

For example, in this site, we want to use the "minimal" install profile for faster install, and using the config-dir option to import our configs after installation. But we're currently hardcoding the "standard" profile and not providing a way to pass alternative options in.

https://github.com/BluesparkLabs/spark/blob/master/src/Robo/Plugin/Commands/DrupalCommands.php#L54

[balintbrews]

Great proposal. Let's be sure we still have a way to run the drupal:install command with sane defaults even when a project doesn't have a drushrc.php file.