Explicitly call stopLoading on the webview in destroyWindow

git-svn-id: http://gtm-oauth2.googlecode.com/svn/trunk@108 22754eea-fc93-e339-b032-c1f495b90c16
Use Google's id_token rather than do an extra fetch for user email; expose +dictionaryWithJSONData

git-svn-id: http://gtm-oauth2.googlecode.com/svn/trunk@109 22754eea-fc93-e339-b032-c1f495b90c16