make layer type optional in props?

[peterqliu]

map.U.addCircleLayer('trees-circle', 'trees', {
    circleColor: 'green', // paint property
    circleRadius: ['interpolate', ['zoom'], 12, 3, 15, 5], // paint property
    circleSortKey: ['get', 'tree-sort-key'], // layout property
    filter: ['!=', 'type', 'stump'], // other property
});

Proposal to make the layer prefix optional in all props. The props above would read color, radius, and sortKey.

Only when disambiguating multiple props of the same kind (stroke- and circle-color in circle layers, icon-, text-, and halo-color in symbol layers, etc) will prefixes be needed. In those cases, the nonprefixed form will refer to the word in the layer type ("color" will refer to circle-color and "width" to line-width)