Implement most of the GeoJSON Simplestyle specification.

Translate the properties "title", "name" (a commonly used non-standard
property), "description", "marker-color", "stroke", "stroke-opacity",
"stroke-width", "fill" and "fill-opacity" into appropriate Marble styles.

Still to do: "marker-size" and "marker-symbol",
presumably just for discrete points, not lines or polygons.

Differential Revision: https://phabricator.kde.org/D23528