[gh-677] Organic Groups update, OG Menu, unl_og theme

This is just a placeholder right now.

We are currently using OG on emergency.unl.edu to restrict a portion of the site for emergency communicators - a use case where different nav or site title is not needed.

For the broader use case we have in mind - say combing all the is.unl.edu sites- we need to add OG Menu, OG Theme, the UNL WDN OG theme that is part of onesite.

We would also want to do a migration with the Migrate module and assign an incoming site to a group.