Elytra Nerf

Only required serverside/singleplayer

- Elytras run out of durability 2x as fast
- Elytras get repaired when you take damage (proportional to the damage you take)
- Balances out durability change
- Incentivizes using explosive rockets!
- Elytras decrease magic damage to .85 when worn
- Elytras go slower when not boosting
- Incentivizes using higher flight duration rockets
- When wearing an elytra you are more end-like (take damage in water/rain)