Privacy Improvement: Closed group's Group Descriptions to inform user of privacy setting

We have seen at least one closed group that was unaware that they were exposing the contents of their group description; that their group description (in addition to the existence/ name of their group) is effectively public although all of the contents (members etc.) are private.

This is additionally important with 2.0: As we take advantage of the handle feature, we have more groups considering the Closed setting so that they can use Loomio's built-in process for membership request/approval.

Curious: maybe there is a way to build this into the app... eg, when Group Privacy selection is Closed, then Group Description editor displays a note that tells the user it is findable on the internet.

@Rob Guthrie