Not calling super UIWebViewDelegate methods was causing issues

The issue with multi-page plugin calls not working, which was [reported on developerforce](http://boards.developerforce.com/t5/Mobile/Handling-cordova-in-the-server-side-for-iOS/td-p/676917), was due to not calling `[super webViewDidStartLoad:]`, which resets a request count variable in Cordova between page loads as part of the re-sync between client JS and native code.