add task system
in vispa many async tasks are used, e.g. zip file extraction. Supply common infrastructure for it.
(from redmine: issue id 2115, created on 2015-01-29 by gmueller)
in vispa many async tasks are used, e.g. zip file extraction. Supply common infrastructure for it.
(from redmine: issue id 2115, created on 2015-01-29 by gmueller)