* Correcting dismissal of dialogs on browser quit.

The IESession object already had code to check that the IECommandExecutor
had fully quit before shutting down the thread on which the executor was
running. However, it had no code to handle the case where all browser
instances for that session were not properly shut down. Now the session
will ask the executor to check one final time and make one last-ditch
effort to dismiss any dialogs and shut down the browser instances. Please
note that the best practice is to handle any alerts that may appear in web
pages being automated before executing driver.quit(); this should only be
used as last resort.
Updating .NET tests.