Rendering settings unification

This PR deals with several issues to make Insight's rendering settings panel look and behave like Web's rendering settings panel. 
Test:
* Check that the arrangement of the UI elements is the same like in Web (order/name of the buttons, etc.)
  (also compare to [Rendering Settings-Preview Pane Round 3](https://docs.google.com/document/d/1aI-od_kCpymL6TX5ydxGbNnVC_LcEjVroL1YsSGD3QE/edit) )
* Check that you get the same behaviour in Insight and Web for undo/redo, copy/paste, and so on.

There is still one flaw: Copy, paste and save actions are not working properly for the renderings settings panel shown in the full image viewer. But they might be hidden anyway, when shown in the image viewer (to be discussed). I'm going to deal with this in a separate PR, as this one is already quite large. 

Not part of this PR (dealt with in follow-up PRs):
* Copy/paste/save problems in full viewer renderings settings panel
* Show ROI Count below preview
* Zoom functionality in preview