Levels update
- Fixed an unintended change to the starting point of w6 in v1.5.17.
- Adjusted 6-7 considering difficulty.
- Changed and Rearranged levels in w7 based on difficulty.
- Changed 7-8, 7-20 (old 7-19), 7-E (old 7-B) and 7-J.
- Moved old 7-E to new 7-19, and old 7-20 to new 7-H.