Backpacks!

Made some changes regarding to how to backpacks (chest minecarts) tps because Mojang doesn't like item displays.

• (1.1.1):
  • Fixed:
    • You couldn't open the backpack when facing down.
    • Sometimes the backpack (chest minecart) wouldn't even tp at all (I needed to remove the tp accuracy to fix this, srry).
    • Now it resets correctly when rejoining on a singleplayer world.

Mostly bug fixes regarding dupes and unintended backpack behaviour.

• (1.1.0):
  • Fixed:
    • You could put the backpack item inside istelf #3.
    • Now the backpack (chest minecart) tps to the player head more accurately.
    • You could steal items from other people backpack if they where moving duping them #4.
  • Added:
    • Added a relocking system because sometimes the backpack would unlock slots #1.

Very small and silly fix regarding to pushing entities.

• (1.0.2):
  • Fixed:
    • You couldn't push other entites #2.

Updated Sentinel library.

• (1.0.1):
  • Fixed:
    • Boats could spawn sometimes.

Adds backpacks to your game in a vanilla-friendly way!