Simplify the styling API

[vojtatom]

After transitioning from BananaGL to MetacityGL, the styling API needs simplification.

The original BananaGL:

gl.style.withAttributeRangeExt("height", 20, 50).useColor([
    0x0088FF,
    0xFF0088
]),

The same style in MetacityGL:

new Utils.Styles.Style().add(
    new Utils.Styles.StyleAttributeRangeExt({
        attribute: 'height',
        min: 20,
        max: 50
    })
).useColor([0x04d3ff, 0xFF00ea])