Confirmed fix for itemframes not showing up. Based on the code in
CraftPainting.
Besids this fix we now pass null itemstacks directly to the
EntityItemFrame to allow the removal of items in ItemFrames.
Hanging entities are placed into the entity tracker and updates are sent
out to clients for the initial placement. Thereafter data watchers are
configured to monitor the item inside the frame. However, if the
direction the ItemFrame facing changes the entity tracker will not send
out updates.
This commit removes and recreates the ItemFrame entity in the same way
that was already done for Painting entities. This causes clients to
be updated appropriately.
If a defensive copy is not used in the API, changes to the item are
reflected in memory, but never updated to the client. It also goes
against the general contract provided in Bukkit, where setItem should be
the only way to change the underlying item frame.
