Don't allow people to remove permissions on themselves

[laurenwalker]

Related to #1442:

Don't allow users to remove themselves as an owner. (This can be configurable - maybe allow admin groups to do so).

This would essentially be a safeguard to prevent people from locking themselves out of editing content. If they need to be removed as an owner, they should be removed by another owner.

We may just want to disable the entire AccessRuleView row for the current user. (Set AccessRuleView.allowChanges to false)