Issue description: Add the White List/Black List toggle on Exporters as well as setting Priority levels.

Why: As a means of getting rid of excess items. The way I imagine it would work is the following:

Say you have an external storage system connected and it has a priority of 50 (so it goes to the external storage first rather then your disks) and your cobble drawer is full and you don't want more cobble stored. Normally the excess would flow into your RF storage system.

To prevent that from happening you could set up a white list filter on an exporter to include cobble. You could then set your grid to -2 priority (what this does is sends makes your grid the lowest priority storage ((if you don't have anything else set lower)) to go to any storage it can with a priority above -2 before it settle into your RF storage system) and set your exporter to 0. Now seeing as your external storage for that item is full it will search for the next highest priority storage which would be the exporter that has cobble white listed and is set to priority level 2.

1. Set up an exporter connected to a block that voids/destroys/whatever.
2. Set it to white list cobble and add the priority level so that it is above your grid storage but below your external storage for cobble (the cobble you want to keep).
3. Once your external storage fills with your set amount of cobble, it will seek the next highest priority storage.
4. Since your internal storage priority is lower then the exporter that has cobble white listed (so it only lets the cobble through of course) it will send the cobble to the block connected to the exporter, destroying it instead of storing it.

This system has some risks of course. If you click black list over white list on accident your internal system will quickly begin voiding your entire internal storage. If you don't set priorities throughout your system correctly it could also begin voiding what you don't want it to void.

Not sure if I'm misunderstanding something but this seems totally possible by just using another external storage?

If you need to remove the items from your disks actively, set it up and run your disks through the disk manipulator with appropriate whitelist settings.

You're right. I set up just another external storage cable with white listed items connected to a trash can with a priority set between where I want it stored and the disks and it sends to the trash.