stackdriver: wip - add very basic checkbox for gce auto authentication

public/app/plugins/datasource/stackdriver/partials/config.html

@@ -31,6 +31,9 @@
       contents will be encrypted and saved in the Grafana database.</info-popover>
   </div>
 
+  <gf-form-switch class="gf-form" label="Use GCE default Authentication" checked="ctrl.current.jsonData.gceAutomaticAuthentication"
+    switch-class="max-width-4" label-class="width-16"></gf-form-switch>
+
   <div ng-if="!ctrl.current.jsonData.clientEmail && !ctrl.inputDataValid">
     <div class="gf-form-group" ng-if="!ctrl.inputDataValid">
       <div class="gf-form">