Apply BuddyPress Group Membership settings to existing Members

[kimwhite]

Is your feature request related to a problem? Please describe.
If access to a new Group is added to the Membership Level, it will only apply to future signups, not to current users holding that membership Level.

Describe the solution you'd like
When an invite or access to a BP Group is added to a level, all existing members should get this access.

Or a separate interface to update Group Access setting to various levels.

[andrewlimaza]

I'd opt-in for a gist to do this, it's something that we need to figure out in core (retroactively doing things) that we can leverage and use across other Add Ons.