Adjust the toolbar w.r.t. the latest UI guidelines

[gr-markin]

As an example we should use the Xcode toolbar:

The following steps have to be done (the first three are basic):

• [ ] Make the toolbar consist of three columns (Left, Middle, Right) in such a way that every column becomes what we have now as a toolbar
• [ ] Design should be the same as on the screenshot
• [ ] Spread existing controls appropriately: "Hide Left" to the left bar, "Hide Right" to the right bar, "Target Selector" into the middle (left alignment), "Play" and "Stop" to the left bar (Note: Ignore for this tasj that play and stop buttons move to the middle whenever the left bar becomes hidden ). Align the buttons within every bar accordingly to the screenshot.
• [ ] Additional: Move "Play" and "Stop" with nice animation to the middle (left alignment) whenever the left bar is hidden