Fix permissions

* performs-writes was mistyped in some places (missing trailing s)
* cascading moderation rules were incorrect in hide & delete: it doesn't make
  sense that someone with elevated (suppress) permissions is unable to delete a
  post/topic (they were correct in restore already)

Added tests

Change-Id: I144c9d19685b08ce186c6bf418faa9b8fb62cab0
Merge "Fix permissions"