Cobblemon: Nests & Dens

Bugfix / Tweaks

• Reworked Den Structure generation to reuse previous den locations (if that den has closed) to hopefully stop the den generation from getting out of control.
  • This should prevent it from generating dens outside world borders (if a limit is used).
• Added check to close a den if all players have left using a third party tool (item or command).
• Fixed issue with Den guardian remaining after den was closed and opened
• Fixed issue with Den would generate the same template everytime it opened