Allow working on Drupal core with simple setup

[shaal]

Is your feature request related to a problem? Please describe

Currently, the only way to work on Drupal core in DrupalPod, is using the special composer.json setup.
But that causes other issues (no drush cr), and other quirks.
Working with the special composer.json setup, should be reserved for specific scenarios only.

Perhaps #46 is going to fix this.

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