Visualize execution history in graphical-editor/viewer

[franzlst]

The last x states of the execution history could be visualized in another color to make it easier for the user to track the execution.

The issue is a duplication of mantis issue https://rmintra01.robotic.dlr.de/mantis/view.php?id=2224.

Originally created by @Rbelder at 2016-03-02 13:49:19+00:00 (moved from RMC internal repository)

[JohannesErnst]

Or maybe give states that were aborted a different color in the execution history so they can easily be spotted when debugging