Switch from JSON to KDL for layout files

[HactarCE]

https://kdl.dev/

Example

widgets {
    circle_chromatic {
        shift -2 -0.5
        radius 1.5
        max_selected_steps 7
        children {
            label "Chromatic circle" {
                shift 0 -2
                font_size 24
            }
        }
    }
    circle_fifths {
        shift 2 -0.5
        radius 1.5
        max_selected_steps 7
    }
    label "Interval Cycle (-1, +5)" {
        shift 0 3.1
        font_size 36
    }
    label "from bo en - My Time" {
        shift 0 2.5
        font_size 24
    }
}