Raster styler todo

[knutole]

Add support for single-raster styling

• should be same type as cube styler (stops)
• should update with cartocss on pile-layer and styleJSON on wu-layer (just like other layers)
• perhaps move styler init to layer.getStyler() to get the proper styler for cube/raster/vector. Also, all ops (saving etc.) should happen on layer, since it's easy to differentiate between them there (ie. layer.setStyle() etc.) We're already doing this a lot, just need to keep this in mind.

  Add support for more stops

• should be possible to add/remove more stops
• cool if opacity could be included in color-picker, instead of input box

  Legends

• frano would like to bring some design-ideas on legend for cube-layers
• need to create a legend for raster/cube layers

[knutole]

closed in favor of https://github.com/systemapic/systemapic.js/issues/200