1.2.26: fix biome height scaling, ground + rootHeight*17

Rebalanced vanilla configs from reteo, accurate biome height scaling.

1.2.23

• [reteo] Support Immersive Engineering, Chisel 2 and Reika's mods
• [reteo] Generate Railcraft saltpeter, firestone and sulfur, again
• [reteo] Rebalance vanilla ore gen
• [reteo] Replaced "Steamcraft.xml" with "FlaxbeardsSteamcraft.xml"
• [reteo] Galacticraft config now generated by Sprocket
• [reteo] Gregtech config runs last
• [reteo] Numerous other tweaks