Major re-organization of handlers. PLEASE NOTE: This drastically affected the Views module API and until modules are updated to match, they will stop working. Efforts have been made to ensure that this won't cause your site to crash, but that's partly up to the individual module as well.

Allow items to specify base tables to skip and create a relationship from upload --> node that will not allow circular relationships.

Some refactoring of how handlers are handled, particularly with their default options. This is an unfortunately widespread change and will affect modules utilizing the API.