Large amount of additions

Hi Sam,
I have added better support for page loading within a html5 site, such as on youtube.  The pageFinishedLoading delegate would not be called after a page has loaded, so I attached an observer to the WebProgressEstimateChangedNotification to call the delegate.

I've also made many changes to the SVModalWebView class to add a navbar and have it's settings controlled by a separate SVWebSettings object.

I was hoping you would like to merge some of these changes when you get the time.

Cheers!
Ben.