R1:52f8756c3c7c

Add a "template" parameter to application default policies

Summary:
Ref T5681. Ref T6860. This doesn't do anything interesting on its own, just makes the next diff smaller.

In the next diff, policies become aware of the types of objects they're acting on. We need to specify which object type all the "Default View/Edit" settings are for so they get the right rules.

For example, a rule like "Allow task author" is OK for "View Policy" on a task, and also OK for "Default View Policy" on ManiphestApplication.