Add visible zoom function

[Gaugi28]

Feature request

Description

As user I want a visible zoom function so that I can zoom in and out and I can see the zoom factor.

Acceptance criteria

• under the cube there is a slider, with it the user can zoom in and out:
  • at the left side there is a minus
  • at the right side of the slider there is a plus
  • the user can pull the slider to the left and the view is zooming out
  • the user can pull the slider to the right and the view is zooming in
• at the right side of the slider there is the zoom factor
• the zoom factor and the slider show always the current zoom factor no matter if the user zooms by mouse, by touch or by using the slider