Add color/size range to display styles

[etatara]

The legacy GIS display has a nice ranged color/size GUI that lets the user specify a set of discrete sizes and colors for the agent style. It would be great to implement this for the other displays in the edited style, since that's a lot more intuitive than the current edited styles.

This would also let us remove the legacy GIS displays since this is a feature of those GIS displays, and the new GIS3D would be virtually indistinguishable.