Add option to export grf file to JSON

[Sowgro]

I added an option to export the data from a game rule file to a json file for use in other applications / tools.
This is a feature I really needed for one of my projects, and I figured it could be useful to other people also.

In the grf editor I added File > Export to JSON to the menubar

Here is a sample of the generated JSON

[
  {
    "Name": "MapOptions",
    "Parameters": {
      "seed": "-5069382193672799790",
      "spawnX": "-62",
      "spawnY": "212",
      "spawnZ": "208",
      "flatworld": "false",
      "worldName": "IDS_ICARUS_WORLD_NAME",
      "worldDescription": "IDS_ICARUS_DESCRIPTION",
      "worldPreviewImage": "WorldSave/Icarus.png",
      "baseSaveName": "Icarus_MG03.mcs",
      "mapSize": "0",
      "themeId": "14",
      "texturePackId": "1031"
    },
    "ChildRules": []
  },
  {
    "Name": "LevelRules",
    "Parameters": {
      "ruleType": "3"
    },
    "ChildRules": [
      {
        "Name": "ActiveChunkArea",
        "Parameters": {
          "name": "Box - 1",
          "x0": "-3",
          "z0": "-23",
          "x1": "-1",
          "z1": "-18"
        },
        "ChildRules": []
      },
(4014 more lines...)

See the sister pull request in -OMI-Filetype-Library