The default registration setting for new Drutopia sites should be Administrators only

Problem/Motivation

New sites that do not check who can register will likely end up with a bunch of bots registering.

Proposed resolution

The default should at the most be "Visitors, administrator approval required" but better would probably be "Administrators only" until an affirmative decision is made.

Remaining tasks

Get this into our feature configuration (or give recipes a try)

User interface changes