Feature/issue 165

Adds functionality that allows the user to whitelist certain potential trackers which need to be whitelisted to work. E.G. Youtube comments. This feature is already present in the chrome version but this would add it to the firefox version. CC @jsha for review. 
Apparently I already made this a function in fact, but somehow this part didn't get refactored to be a function call. Destroying the dialog box is now it's own function.