vdemo

• allow for parallel starting / stopping of components at same level
  different levels are handled consecutively
• even different groups can be started / stopped in parallel
• individual components start / stop in between too
• start / stop within same group conflicts with each other -> cancel a running command
• gui feedback on group commands
• removed level command buttons
• removed obsolete -c option: components are checked in 1s intervals at most
  time required for checking, adds on top of this
• option -w defaults to 5s (timeout for successful component start)

If you observe strange start order, check your levels!
Before, components were started in given order, -w option specifying to wait for a component before proceeding to the next.
Now, all components on the same level are started in parallel. -w option simply states the timeout period, before we give up to wait for this component to be ready.