Allow Herald Adapters to choose applicable rule types (global, personal, etc).

Summary: Ref T4264. Lays the groundwork for new "Object" rule types. Prevents personal "Hook" rules, which don't make any sense.

Test Plan: Created new Maniphest (global/personal available) and Ref Hook (global only) rules.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4264

Differential Revision: https://secure.phabricator.com/D7852