Implementing of preparation mechanism of WebDriver quit/close methods.

Helpful for next situation:
- Need to close window with pop-up confirmation of exit. Example (try to close that window):
http://samples.msdn.microsoft.com/workshop/samples/author/dhtml/refs/onbeforeunload.htm
AND
- IE capability 'unexpectedAlertBehaviour:ignore' used

Jira link:
https://java.net/jira/browse/THUCYDIDES-254

PROBLEMS:
- some tests in WhenUsingAWebDriverProxy class may be failed. Need to edit tests conditions and asserts (I have no idea)