Pyrellium

This update alters world generation, be sure to back up your world when updating

• Added Packed Black Ice
• Significantly adjusted the generation of Frostburn Valley
• All Pyrellium flora can be composted now
• Improved the handling of nether carvers for the replace_wall feature
• Added a 5% chance for skeletons in the nether to spawn with amethyst/opal arrows (configurable)
• Added a config option to disable the freezing effect from standing on black ice