Spigot Patch: Add option to modify hopper cool downs

This commit allows the server admin to edit the default hopper cool down
time (default: every 8 ticks), so the hoppers can check more often or less
often (to save resources).
It also adds a configurable check cool down which fixes idle hoppers to be
checked every tick causing huge lags on servers with many hoppers.

https://github.com/SpigotMC/Spigot-Server/commit/a0a21b3c9e35019040be9eab069688cb4bd5d579