progression tweaks, balance changes and QOL

• reworked slabs and stairs
• added vertical slabs
• added copper armor
• buffed wandering traders
• made structures spawn less frequently
• wandering traders now buy items and sell maps
• deepslate now requires iron or better to mine (excluding ores)
• deepslate ore will now sometimes drop double the ore
• added a reroll to the enchantment table
• fixed bed recipe to use 7 wool rather than 19
• changed cobwebs slightly
• raised rate at which you collect XP