Spool Holder for RailCore2

**Update:**

So I found a spool that was slightly bigger, and it dragged against the electrobox, so I've added a new model that's slightly elevated.

Look for an update to the filament guide thing, as well; it keeps popping out, so I'm going to make it taller and tighter.

**/Update**

If you're clumsy like me, and keep knocking the spools off the skate-bearing spool carrier we recommend with the RailCore, this might be a quick-n-dirty solution. I'm using it now and it seems to work f