Correct bugs in Treasure Hunt code, add new landmarks

This corrects a few treasure hunt bugs -
- Incorrect direction given on steps in some cases
- Cache chest not correctly buried
- Typos and punctuation issues in clues
- "v1.8-compatible book pages"
- new landmarks: fairy ring, flower garden, memorial
- relighting was not being done
- cottage construction improved (floor still missing, though)
- make stone type used for landmarks change with biome
- allow greater step size for treasure hunts (up to 40 chunks instead of 20)