feat: basic implementation of kml support

Close #23

Author: paodb

src/main/java/com/flowingcode/vaadin/addons/googlemaps/GoogleMap.java

@@ -338,6 +338,24 @@ public void setControlSize(int controlSize) {
   public int getControlSize() {
     return this.getElement().getProperty("controlSize", 0);
   }
+
+  /**
+   * Sets a KML or GeoRSS feed url to be displayed as a KML Layer in the map.
+   * 
+   * @param url to be displayed.
+   */
+  public void setKml(String kml){
+    this.getElement().setProperty("kml", kml);
+  }
+
+  /**
+   * Returns the current  KML or GeoRSS feed url associated with a KML Layer in the map.
+   * 
+   * @return the current url.
+   */
+  public String getKml() {
+    return this.getElement().getProperty("kml");
+  }
 
   public static class GoogleMapClickEvent extends ClickEvent<GoogleMap> {
     private final double lat;