Allow different config directory definition

[b-sharpe]

When running acquiaConfigUpdate it assumes 'sync' as the config directory definition:
->drush(['config-import', 'sync'])

Would be great if this could be configurable from the extraconfig or the likes, Acquia for example uses 'vcs' as the default.

[typhonius]

That's a good idea, I'm working on some enhancements to this part of the code to make drush steps optional (since some users run these as part of an Acquia Cloud hook) so I'll look to adding in this functionality alongside.

[typhonius]

I've added these in 0a57491. It's probably almost time to tag another release which these changes will be in.