Make things configurable

[jover]

There're a bunch of assumptions regarding paths & locations of folders which are setup by default by Drupal-Scaffold.

This should be configurable so it's possible to use this project with a different folder structure.

More specifically:

• $allowed_extensions
• $excluded_paths

[mfernea]

I would also add a configuration for using or not the Beautifier, as it sometimes messes things up.