L4D2: Dynamic Difficulty plugins added

I have added 2 new plugins to regulate the difficulty depending on the number of players on the server:

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• Special Spawn Regulator (modded by Joker)
  
  

Plugins are currently installed on

• alServ2016
  
• alServ2017
  
• alServ2018
  
• alServ2019
  

The modded version additionally sets the SI health depending on the number of players on the server.
The config values are near the default at the moment.
So some adjustments may occur here and there.