Allow admins to configure which content types should allow conflict resolution

We probably want a way to let admins control if conflict.module "hijacks" the node edit form for each content type. Perhaps inject a node type setting into the "Submission form settings" vertical tab? Seems silly to add a whole new vtab for this, although I'm not sure people would know to look in "Submission form settings" since this is really about "Edit form settings" (which is mostly the same, but subtly different). Maybe just in "Publishing options", although again, that's not exactly the right fit, either...