Create: Let The Adventure Begin

I finally documented the changes properly so here is the full change log instead of the my normal summarization!

• Added new advancement

• Added roads to birch structure

• Added decorations to big plains structures

• Added 13 new decorations

• Added 2 new loot tables

• Changed name and description of the advancements

• Changed all the normal loot tables

• Changed how every spawn to make structures more balanced and common (from an average of 1 structure per 700700 square to 1 structure per 500500 square)

• Changed design of: the castle, birch structures, cherry house, every big plain structure, quarry and grot

• Removed both end structures