public ObservableList<Section> getSections() {
        if (null == sections) { sections = FXCollections.observableArrayList(); }
        return sections;
    }
Returns an observable list of Section objects. The sections
will be used to colorize areas with a special meaning such
as the red area in a rpm tile. Sections in the Medusa library
usually are less eye-catching than Areas.

@return an observable list of Section objects
src/main/java/eu/hansolo/tilesfx/Tile.java