Nether, Ender Dimension Ore Fixes

- Nether Ores were not generating in the Nether. They should now. Ender
Ores had the same problem but should be fixed now too. (I gave the
Nether and End their own Custom Ore Cluster Preset unique from the
Overworld.)

- Eximite (Ender Ore) was generating in the End as Copper. It was a
wrong reference in the original config file. Fixed now.