Prevent the browser from opening popups to external sites. Issue #122

We decided to prevent each crawler from firing events that open an external popup - in a very similar fashion to how the crawler does not fire events that open external websites. Our test includes HTML pages that open popups to internal and external sites and a java test that uses the HTML pages and checks if the candidate list contains external sites. (L2C5 from ECE 310 course of Prof. Ali Mesbah)