OG Visibility

Enables defining default group content access at the group level. Provides 3 visibility settings:

1. Public: Group is public and group content is public by default
2. Private: Group is public and group content is private by default
3. Hidden: Group is private and group content is private by default

It provides an easy way for content editors to create groups everyone will be able to see they exist, but where only group members will be able to access content inside these groups.