Streamline and document the review procedure

Over time, we've adopted a bunch of unwritten rules and customs. This can lead to confusion for both us and outsiders at times.

This is an attempt to streamline and informally document the review process and the way we work. It documents the review process, and introduces the concepts of Control Reviews and Group Notices to keep apps in check. These are things we've done before under slightly different names, and without any established rules.

Let me know what you think.