Haf creates unused table columns and indexes in non-forking apps

Motivation: this issue came up in the context of hivemind, which is a non-forking app.

HAF creates the hive_rowid column in the app's tables. It also appears to create an index on this row_id in at least some cases. I suspect that this row and index is unneeded in non-forking apps. It seems almost certain the index is at the very least, as it is shown as "unused" on our production server for many hivemind tables.

The argument for keeping is it would be easier I suppose to upgrade an existing app database from non-forking to forking, but this doesn't seem to be worth the cost.