More ORS 1.3 changes

This adds three more optional fields to the planetary resource nodes.

The low and highColor values can be used to specify color ranges for map overlays; these work the same as how Kethane resources define their colors.

The other is a hidden flag, which will simplify making resources not meant to be displayed on overlays. It could also be used to prevent ORS scanners from detecting them, but that will require changes to the ORS scanner module. It defaults to false, so it doesn't need to be included in the resource definition unless you want to flag something as hidden.