REP-819 Keystone V3 Filter

The mess that is Keystone v3! Comment on _everything_ so we can get this fixed up. =)
Quick question: does the "WWW-Authenticate: Delegated" header need to be removed? That is, should that particular value be stripped when we insert the keystone value, or is that something the end user should see? In the v2 filter, it was being stripped along with any other values of that header.