Custom Respawn Locations, Bugfixes

Admins can now add a custom respawn location for both winners and losers in a duel, allowing for edge functionality.

New Features:

• Added 'winner_return_location' config.yml option.
• Added 'loser_return_location' config.yml option.
• Added 'custom' option to both 'return_winners' and 'return_losers'.

Bugfixes:

• Fixed bug where 'previous' respawn option returns player to arena spawn point instead of previous location.
• Fixed placeholder error with duel announcements both'%player_one%' placeholder is repeated twice.