Working around the Friends Access comment bug

Elgg has a major bug (#3391) due to friends not being a real ACL. Basically the access controls are messed up on comments left on ACCESS_FRIENDS content. Each comment will only be seen by friends of that commenter

The solution is quite difficult and won't be tackled until at least 1.10, so I'd like to create a plugin we can all use to work around this very annoying issue.

Proposal: When comments or likes are created, the ACCESS_FRIENDS value is changed to ACCESS_LOGGED_IN. This presents a small, but managable info leak: These comments will show up in searches, but the container commented upon will be protected. Filters in the river views will hide the river entries when the container should not be seen.

Also, we should update the access_id on comments/likes/river entries when the container has its access level changed, to fix a similar bug.