Lots o' Improvements!

Various Changes

• Removed prefix from island-top header messages for simplicity, can be added back manually in message.json.
• Set the /is go location using the new /is set-go command.
• Island Chest opening message is now actually sent.
• Island Creation cooldown, configurable, default 6 hours.
• Actually teleport players back to default world on island deletion.
• Visitors can no longer access chests.
• Reconfigured Gradle, reduced binary size from 5.2 mb -> 2.2mb
• Remove Islands from /is top on deletion.
• Changed description for /is in /help SkyblockX
• Deny cross island enderpearls
• Require the skyblockx.reset permission to reset islands.
• Fix struct file saving with specific items in chests.
• Fix default world teleport on damage
• Improve startup log