Summary:
Ref T13661.
I'm fairly sure these policies don't actually do anything (you can't "interact" with a blog) but the primarily support a Phame Post object policy of "Same as Parent Blog", which is the "natural" interact policy for a post.
Most of this is infrastructure support for mutable interact policies: today, only Maniphest has interact mutability and only via indirect effects (locking tasks), not through a directly mutable "Can Interact" policy.
Test Plan:
Ran storage upgrade, edited interact policy of a blog, saw appropriate persistence and transactions.
Created and edited a task to make sure there's no weird fallout from increasing what can be done with interact policies.
Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam
Maniphest Tasks: T13661
Differential Revision: https://secure.phabricator.com/D21751
