Support line/polygon type geometry printing

[sanak]

Problem
I haven't checked this actually, but from the following code part, only point type geometry printing seems to be supported now.
https://github.com/gtt-project/redmine_gtt_print/blob/1.1-stable/lib/redmine_gtt_print/issue_to_json.rb#L211-L227

style: {
  val1: "#FF4500",
  "*": {
    symbolizers: [{
    fillColor: "#FF0000",
    strokeWidth: 5,
    fillOpacity: 0,
    graphicName: "circle",
    rotation: "30",
    strokeDashstyle: "solid",
    strokeLinecap: "round",
    type: "point",
    graphicOpacity: 0.4,
    strokeColor: " ${val1}",
    pointRadius: 8,
    strokeOpacity: 1
  }]},

Improvement
It would be nice to support line/polygon type geometry printing.
https://mapfish.github.io/mapfish-print-doc/styles.html#stylev2
https://github.com/mapfish/mapfish-print/tree/master/examples/src/test/resources/examples/json_styling

[sanak]

Alternatives
Something style JSON configuration in plugin's setting view may be good alternative like GTT plugin's geocoder option.