Crazy Envoy

Hello, this update fixes a couple bugs and adds some requested features.

Bug Fixes:
  - Snow Layer(Not Block) Blocks get replaced with the crate instead of
landing above it.
  - Players in Spectator Mode can open crates.

Added:
  - PlaceholderAPI placeholder support.
https://www.spigotmc.org/resources/placeholderapi.6245/
  - Option to set how high the falling blocks spawn. (Good for the
Nether)
  - Add an option so the broadcasts are a per world based message.
  - Random prize bulk. You can now get multiple prizes from one envoy
crate.