feat(AgmMap): recentering for triggerResize

When you call the triggerResize method of AgmMap, the map gets recentered
automaticaly.

Closes #789
Closes #976

BREAKING CHANGES

Recentering of the map after triggerResize call is now the default behavoir.
You can have the previous behavoir with triggerResize(false).

src/core/directives/map.ts

@@ -395,15 +395,22 @@ export class AgmMap implements OnChanges, OnInit, OnDestroy {
 
   /**
    * Triggers a resize event on the google map instance.
+   * When setCenter is true, the setCenter method of the google map gets called with the current lat/lng values.
    * Returns a promise that gets resolved after the event was triggered.
    */
-  triggerResize(): Promise<void> {
+  triggerResize(setCenter: boolean = true): Promise<void> {
     // Note: When we would trigger the resize event and show the map in the same turn (which is a
     // common case for triggering a resize event), then the resize event would not
     // work (to show the map), so we trigger the event in a timeout.
     return new Promise<void>((resolve) => {
-      setTimeout(
-          () => { return this._mapsWrapper.triggerMapEvent('resize').then(() => resolve()); });
+      setTimeout(() => {
+        return this._mapsWrapper.triggerMapEvent('resize').then(() => {
+          if (setCenter) {
+            this._mapsWrapper.setCenter({lat: this.latitude, lng: this.longitude});
+          }
+          resolve();
+        });
+      });
     });
   }