Delete hook and function

It would be very useful if MultiBlock could expose an instance delete hook (called during the multiblock_delete() function) that MultiBlock-enabled block modules could use to extend functionality when instances are deleted (e.g. when an instance of a module's block is deleted, the module using the hook could also delete references like the instance's variable(s) or row(s) in a custom table).

On a related note, it would also be useful if there was an exposed function (e.g. multiblock_delete_all_block_instances($module, $orig_delta) that could be called from a MultiBlock-enabled block module's hook_uninstall) that loops through all of the instances associated with the module/original delta and calls the multiblock_delete() on each returned instance.