Add missing Google Maps Data Layer API

Fixes #2249.

- Add a `data` property to the `Map` class.
- Add Google Maps test file and Data Layer API tests.
- Add the following classes and interfaces which form the Data Layer API:

  - `Data`
  - `Data.DataOptions`
  - `Data.GeoJsonOptions`
  - `Data.StyleOptions`
  - `Data.StylingFunction`
  - `Data.Feature`
  - `Data.FeatureOptions`
  - `Data.Geometry`
  - `Data.Point`
  - `Data.MultiPoint`
  - `Data.LineString`
  - `Data.MultiLineString`
  - `Data.LinearRing`
  - `Data.Polygon`
  - `Data.MultiPolygon`
  - `Data.GeometryCollection`
  - `Data.MouseEvent`
  - `Data.AddFeatureEvent`
  - `Data.RemoveFeatureEvent`
  - `Data.SetGeometryEvent`
  - `Data.SetPropertyEvent`
  - `Data.RemovePropertyEvent`

googlemaps/google.maps-tests.ts

@@ -0,0 +1,107 @@
+// Test file for Google Maps JavaScript API Definition file
+/// <reference path="google.maps.d.ts" />
+
+var map = new google.maps.Map(document.querySelector("☺"));
+
+/***** Data *****/
+ 
+new google.maps.Data();
+new google.maps.Data({ map: map });
+ 
+var latLng = new google.maps.LatLng(52.201203, -1.724370),
+    feature = new google.maps.Data.Feature(),
+    geometry = new google.maps.Data.Geometry();
+
+var data = map.data;
+
+data.add(feature);
+
+data.add({
+    geometry: latLng,
+    id: "Test feature",
+    properties: {}
+});
+
+var isIn: boolean = map.data.contains(feature);
+
+data.forEach((feature: google.maps.Data.Feature) => {
+    console.log(feature.getId());
+});
+
+var map: google.maps.Map = data.getMap();
+data.setMap(map);
+
+var style = data.getStyle();
+data.setStyle(style);
+
+data.setStyle({
+    clickable: true,
+    cursor: "pointer",
+    fillColor: "#79B55B",
+    fillOpacity: 1,
+    icon: {},
+    shape: { coords: [1, 2, 3], type: "circle" },
+    strokeColor: "#79B55B",
+    strokeOpacity: 1,
+    strokeWeight: 1,
+    title: "string",
+    visible: true,
+    zIndex: 1
+});
+
+data.overrideStyle(feature, { visible: true });
+
+data.revertStyle(feature);
+
+data.addGeoJson({});
+data.addGeoJson({}, { idPropertyName: "Test feature" });
+
+data.loadGeoJson("http://magicGeoJsonSource.com");
+
+data.loadGeoJson(
+    "http://magicGeoJsonSource.com",
+    { idPropertyName: "test" });
+    
+data.loadGeoJson(
+    "http://magicGeoJsonSource.com",
+    { idPropertyName: "test" },
+    (features) => {
+        for (var i = 0, len = features.length; i < len; i++) {
+            console.log(features[i].getId());
+        }
+    });
+
+data.toGeoJson((feature) => { });
+
+var dataMouseEvent: google.maps.Data.MouseEvent = {
+    feature: feature,
+    latLng: latLng,
+    stop: (): void => {}
+};
+
+var addFeatureEvent : google.maps.Data.AddFeatureEvent = {
+    feature: feature
+};
+
+var removeFeatureEvent: google.maps.Data.RemoveFeatureEvent = {
+    feature: feature
+};
+
+var setGeometryEvent: google.maps.Data.SetGeometryEvent  = {
+    feature: feature,
+    newGeometry: geometry,
+    oldGeometry: geometry,
+};
+
+var setPropertyEvent: google.maps.Data.SetPropertyEvent = {
+    feature: feature,
+    name: "test",
+    newValue: {},
+    oldValue: {}
+};
+ 
+var removePropertyEvent: google.maps.Data.RemovePropertyEvent = {
+    feature: feature,
+    name: "test",
+    oldValue: {}
+};