Consider removing the acl:origin feature

[michielbdejong]

I think acl:origin was useful when WAC was combined with WebID+TLS, but now that the Solid project combines WAC with Solid+OIDC, I think it has lost its meaning and it would be better to remove it. Not sure what the upgrade path would be, and I'm not proposing we work on this now, I just wanted to document that this would be a thing to consider, and leave this issue open for when people in the future develop WAC further.