No Crawling and Old Sneak behaviour

- added a server config for old crouching eye level (1.54 blocks). this may clash with nostalgic tweaks' "oldSneaking" tweak, so both options shouldn't be used at the same time
- fixed player getting stuck in standing or crouching position after a trapdoor is shut on the player's head
- fixed a bug with ladders where players could phase through blocks if crouching and then standing up again. this fix changes the crouching height from 1.65 to 1.8 blocks, which is the same as standing height, but as far as i know, no block is in that specific height range other than maybe snow layers (but who really uses them in that way anyway?)