Oregen correction pass Part 1

Implements RR2-style oregen. RR3 enhancements are not part of this section of the pass.

Note that Nether Ores have had their mining levels adjusted as part of this pass. They are tuned to be one step more difficult to mine than their standard counterpart in nearly all cases.

Copper and Iron have had their upper spawn limit raised to y80 from the y60 limit in RR2, with their spawn frequency adjusted to match.