using AgsThreadPool by GUI feedback

The GUI feedback slows down the entire application and is therefore a bottle-neck. The thread pool is believed to give some performance boost.

The situation for now is that every tic of AgsDevout a task is executed. This task creates everytime a new thread. It's well known that creating threads is computing expensive work. That's why the task code should use the thread pool instead of instantiating every tic a new thread.

To be continued ...