Fix %worth% plaecholder, AsyncPlayerChatEvent, and Citizens trait

[BlackBeltPanda]

Just some minor updates:

• Reduce some extra calls to getInventoryWorth
• Call setOpenPage prior to updating the page view for a player when using the sell GUI, otherwise getopenpages returns null
• Change AsyncPlayerChatEvent priority to LOWEST since we don't need to know if other plugins tried to cancel it. This way, other plugins can see that we cancel it and won't try to format the message in chat.
• Deregister the Citizens trait on plugin disable to allow the plugin to be reloaded.

[Huskehhh]

Cheers for the PR :)