R1:42383214ea1e

Enable admin to view and delete other users' herald rules

Summary:
enable admin to delete user's herald rules. This is useful for
managing non-active users' rules. For example, ex-employees' rules. The
code change includes:

- Added a 'All' tab which is only accessible to admin.
- Refactor out a HeraldRuleListView which is used by both the home
controller and the all rule controller

Test Plan:
delete an ex-employee rule as an admin; disable myself as
admin and verified that I don't have access to…