Refactor to create StyleProperty class

[lucaswoj]

There are many methods within StyleLayer that only operate on a single style property.

• setLayoutProperty
• getLayoutProperty
• getLayoutValue
• setPaintProperty
• getPaintProperty
• getPaintValue
• getPaintValueStopZoomLevels
• getPaintInterpolationT
• isPaintValueFeatureConstant
• isLayoutValueFeatureConstant
• isPaintValueZoomConstant
• ...

A cleaner design would be to have a StyleProperty object per property with all of these methods

type StyleValue<T> {
  isZoomConstant: boolean;
  isFeatureConstant: boolean;
  calculate(zoom:number, featureProperties: {}) => T;
  getInterpolationT(zoom: number) =>;
  ...
}

At the same time we might make StyleTransition conform to the same interface as StyleProperty

ref #2629 (comment)

[jfirebaugh]

👍 -- what gl-native does might serve as a model here:

• PaintProperty
• LayoutProperty
• PropertyValue