Changelog

Features:
- advanced battlement, platforms (big radius)
- new roof piece

New blocks:
- RoofTileLargeRound
- StonePlatformRoundLarge
- StoneBattlementRoundLargeCenter

Fixes:
- fixed cannot step onto wooden floor from spiral stairs
- fixed particle effects LODs missing (major source of a slowdown)
- fixed few crashes here and there