Change enable/disable groups to just act on memberships

• No longer send group delete/add events to change log
• No longer run hooks for group delete/add
• No longer disable attribute assignments
• No longer make certain queries not return the group if disabled

The idea is that the only impact on a disabled group is that the memberships on the group are disabled.

This would still send a change log event for the group being disabled/enabled and consumers can do something with that if they choose.