This commit implements radial gradient as background and adds the option
to settings. It also renames "Color gradient" as "Linear gradient",
keeping Linear gradient default. Internally, it remains unchanged for
compatibility.
Radio gradient is more suitable for CAD, since it gives a more balanced
color distribution across the screen, improving visibility of model and
sketches with a halo-like effect.
- when finding a suitable background color gradient, it is annoying that there is no button to switch the begin/end color of the gradient. With the button one can quickly see the the changes and find a suitable gradient much quicker
- when finding a suitable background color gradient, it is annoying that there is no button to switch the begin/end color of the gradient. With the button one can quickly see the the changes and find a suitable gradient much quicker
