Task:VProcess(): public: return new_active_task_objekt
  This virtual method is for active part of the task. In this class it only
  waits for key pressing and the ends. It should be redefined by derived
  classes for doing required job. The return value can be another object
  derived from the task class and it becomes active. This enables the task
  chaining, to estabilish conections between the objects (which enables
  multi-threading). See the instvar variable DoneBlock. This method must be
  finished when receiving the nSwapTask code (255) from the keyboard
  and must be resartable. For task finishing is used method Done().