Improve FoodLevelChangeEvent. Adds BUKKIT-3581

Split from GlowstoneMC/Glowkit#3
Original Bukkit PR: Bukkit/Bukkit#1070
Additional changes: Documentation changes (minor)
Glowstone implementation: Not done

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Previously, FoodLevelChangeEvent only provided the player involved in the
event and the new food level of the player. This changes the event to also
provide the type of food being consumed, along with the new saturation and
exhaustion levels of the player.