code: function Blocker(config, logger) {
  
          //DB must define an add, remove and contains function!
          if(!(config.db && config.db.add && config.db.remove && config.db.contains)){
              throw "db must define an add, remove and contains function";
          };
  
          _config = config;
          _logger = logger;
      }
docs: The Blocker class realizes an IP blocklist that allows other modules to block attackers.
  @param config must contain at least an object named db that must have an add, remove and contains function.
  Furthermore it allow the user to specifiy a blockTime. If blockTime is not set, entries will never be removed
  from Blocklist.
  @constructor