Add custom radiobuttons for nicer look and cross-platform consistency

[israel-dryer]

This is a potential improvement to create a consistent look & feel across platforms. Currently, the native windows buttons are used on windows, and standard clam theme on linux & mac. Also, these custom buttons look like the Bootstrap styled buttons on bootswatch.com, so that's a plus.

I could create images for the hover and pressed effects, as I did for the scale indicator, but not sure if it's strictly necessary.

light theme example

dark theme example

[israel-dryer]

example of new radio buttons on the lumen theme

example of the new radiobuttons on the cyborg theme

[israel-dryer]

The style works well on light themes.. I'm not completely sold on the look for dark themes. Possibly I could make the colors inverse for background and indicator? It is consistent with the look on bootswatch, but that's not necessarily a reason to keep it.

[israel-dryer]

This uses a light background for the off color, so the look is more consistent.

[israel-dryer]

Inverse colors with a larger indicator

Inverse colors with a smaller indicator

[daniilS]

All those options look great! A slightly scaled down version with the large indicator is probably the closest to the native radiobutton.