Include deletes in the change list

[donno]

Currently if a user deletes something, other users who have already loaded
the page don't see the object disappear until they force a browser refresh.

This could very easily be implemented by having a "deleted" column on the
geometry table instead of actually deleting the row. This has the
added benefit of making it so data is not lost.

This could then be picked up as a "change" and the web interface could
see that it was deleted and remove it.