switched from CTR to FF notification box

This PR replaces/removes the Classic Theme Restorer extension, which allowed us to use the Add-on bar which was removed in Firefox 29, with basically the same functionality being provided by Firefox's "notification box". Hat tip @miohtama for pointing out this possibility, thanks! See https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XUL/notificationbox for some basic info.

As of now it still needs improvement, in particular: the icon on the bar needs to be better. Also I'm noticing a javascript error that comes up in the console for each audited page (doesn't affect functionality but want to know what it is/remove it). A bit more tidying up in script.js may also be helpful.

Worth emphasising that even if there is some slight disadvantage, it is *highly* desirable to remove the dependence on CTR (which we simply bundled in as a stopgap). So far I don't see a meaningful disadvantage (another advantage I note is that in the old version, the user closing the addonbar would simply stop the buttons being available for the rest of the audit I believe, whereas here the next notification bar will still come up if the previous one was closed).

This PR is *not* yet ready to merge, as it hasn't been tested sufficiently, but I put it here so that others can try it and report feedback. Thanks.