[Bleeding] Fix logic for calculating slot in Creative mode. Fixes BUKKIT-4715

Previously, hotbar slots for player inventory would return 9 - 18 while in
Creative mode, rather than 0 - 9. This commit fixes the logic used for
calculating the returned slot based on the raw slot.
Add methods to get and set knockback strength in Arrow. Adds BUKKIT-5103
Add setCritical and isCritical methods to Arrow.java. Adds BUKKIT-5113
[Bleeding] Add ProjectileSource interface. Addresses BUKKIT-1038, BUKKIT-1156
[Bleeding] Add setCharged and getCharged to WitherSkull. Adds BUKKIT-3060
POM Changes
Measure Timings Duration
Timings Paste Command
Enchanced Timings
Add PlayerItemDamageEvent
BungeeCord Support
Add Arrow API
Add Particle API
Define EntitySpawnEvent and SpawnerSpawnEvent

Defines EntitySpawnEvent and SpawnerSpawnEvent. Adds BUKKIT-267 and BUKKIT-1559
Entity Mount and Dismount Events
Update Depends

- All of these changes have been reviewed to be binary compatible and in general contract compatible with previous versions of the libraries.
InventoryClickEvent getClickedInventory

Add InventoryClickEvent.getClickedInventory. Adds BUKKIT-4495
Plugins currently have to do the logic themselves on the raw slot ID
in order to determine the inventory clicked. This provides the logic for plugins to
readily identify which inventory was clicked.
Added getAllSessionData() to the Conversation API.
Catch Conversation API Errors
Player Collision API