Issue: Rebuild forum cache too much

Every time an article is edited the forum cache is rebuilt. This can be an intensive process for many boards. The cache is only rebuilt so that the "vault_lastthread" and "vault_lastedit" values can be updated. When should be using the forum counters fetch called by "cache_ordered_forums" to account for this unbuilt data. In the short run (since these values constantly update it should be the short run anyway), this would be much easier on the server.

Fixed for the next build.