doDelete() needs to invalidate instance cache

[hans]

When objects are deleted from the database, we need to remove them from the instance cache / identity map.

A doDelete() call with a single object need only invalidate that single entry from the cache. A doDelete() call with Criteria is probably better off either invalidating the entire set or performing a query and invalidating each match individually (that sounds like a horrible idea).

[hans]

In changeset:424, the behavior of retrieveByPK() was changed so that the database is always consulted when fetching content. This fixes this issue; however, there is still a danger in the instance map growing without bound, so we may still want to remove single instances from the map when we know they have been removed from the database.

[hans]

Closing this. Comment on flushing cache added to ticket:280.

[francois]

also fixed in 1.3