Fix PlaceholderAPI integration

[FireML]

• Removes a redundant method
• The broadcast(CommandSender) method now sets the relevantPlayer variable when broadcasting
• The broadcast() method now creates a copy of the message class, and uses the broadcast(CommandSender) method on the copy

We create a copy when looping over all players to keep the original placeholders intact. All players now get placeholders related to themselves.

[FireML]

I forgot something and will do it tomorrow.