styled rasters

[incanus]

Now that we have raster tiles (#70), when we get data sources (#101) we should provide for styling rasters (color tint, saturation, etc.)

[incanus]

Waiting on #343 now.

[lbud]

Per spec, should support

  "class_raster": {
    "raster-opacity": {
      "type": "number",
      "default": 1,
      "transition": true
    },
    "raster-hue-rotate": {
      "type": "number",
      "default": 0,
      "function": true,
      "transition": true,
      "doc": "Rotates hues around the color wheel by the specified number of degrees."
    },
    "raster-brightness": {
      "type": "array",
      "value": "number",
      "length": 2,
      "default": [
        0,
        1
      ],
      "function": true,
      "transition": true
    },
    "raster-saturation": {
      "type": "number",
      "default": 0,
      "function": true,
      "transition": true
    },
    "raster-contrast": {
      "type": "number",
      "default": 0,
      "function": true,
      "transition": true
    },
    "raster-fade": {
      "type": "number",
      "default": 0,
      "function": true,
      "transition": true,
      "doc": "Duration of the fade when a new tile is added. @TODO rename?"
    }
  }

Looks like right now we've only got opacity.

[lbud]

closing per #418