Add example to repository that shows how to composite and color the GroundWater.cdb dataset from pycinema-data repository

[dhrogers]

We should have an example of a pipeline that shows how to color and composite both components of the GroundWater dataset (shown below in the 'explore' application). This doesn't have to work within the 'explore' or 'view' applications, but it should show how to hook up something that allows the user to control the color of more than one image element.