Possibility to use existing tasks as template.
Wording
Simplified main window controls.
Allow to change max parallel tasks.
Allow to add task when sidebar in focus.
Show termination signals and improve coloring.
Python 3 compatibility
Allow to set task niceness.
Control for niceness.
Disallow empty command (and indicate that).
Use just an 1 increment in niceness test.
Allow to terminate unstarted tasks.
Intelligent default for max parallel tasks.
Added missing test for joining tasks.