"Group is out of sync" warning on login

[psikoi]

Copied from dekvall/runelite-external-plugins#77

When a player logs in, we should compare their in-game clan members list with WOM and if they differ, we should show a chat message saying it's out of sync and suggesting they use the sync feature.

This would relieve some responsibilities from clan admins, they wouldn't have to remember to sync, we would tell them when they need to.

This would require #1 to be implemented to make sure people don't get this message when they log in to an account in another clan and blindly follow this warning and end up overriding their entire group members list on WOM.

Note: I can't remember if the clan members list is accessible on the client without opening the interface, so we should find that out first.