Provide UI for removing raster layer

[syntagmatic]

[emilyhobson]

@nicolettehayes Can you mockup and reassign to @syntagmatic ?

[syntagmatic]

There's a little box that pops up when selecting a raster layer. The Info/Close buttons could perhaps go in the top right corner of that box. Or in the dropdowns somewhere on the right side.

http://stamen.github.io/ecoengine/explore/

[syntagmatic]

Added red x button next to date picker http://stamen.github.io/ecoengine/explore/