reworked task allocation for pathfinder workers

- each pathfinder can now handle more than 1 client, default is 5
- a pathfinder is only spawned if there are no available slots in the
already active pathfinders
- this drastically reduces the amount of pathfinders required to handle
a greater number of tanks
max active bots cap raised from 20 to 50 (due to worker load balancing changes)