Move registration of App plugin from config.xml -> code

Less fragile this way.

framework/src/org/apache/cordova/CordovaWebView.java

@@ -157,6 +157,7 @@ public class CordovaWebView extends WebView {
         exposedJsApi = new ExposedJsApi(pluginManager, jsMessageQueue);
         resourceApi = new CordovaResourceApi(this.getContext(), pluginManager);
 
+        pluginManager.addService("App", "org.apache.cordova.App");
         initWebViewSettings();
         exposeJsInterface();
     }