Soul Graves

Special thanks to Catnies for their contributions!

• Add Custom Event API (Thanks to Catnies)
• Add BoostedYAML for proper config management
• Add permission soulgraves.spawn for spawning a soul and an accompanying config option if we should check permissions for spawning a soul (Thanks to Catnies)
• Fix KeepInventory spawning a soul (Thanks to Catnies)
• Fix server crash when trying to spawn a soul above the build limit (Thanks to Catnies)
• Fix sending message when the message is left blank (Thanks to Catnies)
• Fix spawning a soul when there is no XP or Items in the player's inventory (Thanks to Catnies)