Introducing the CSP Fixer

@devoncarew

Devon: sorry, a couple of unrelated trivial changes have crept in.

I should also add tests.

Also note that I deliberately exposed the feature only in the form of an explicit action. I didn't want to build it into the Bower install/update sequence or anything like that because it's too early and too risky.

Yep, I've been thinking about that.

Possible approaches:

1. Run just the CSP checking part of CspFixer in background and see if it would actually fix something if it ran for real. If yes, suggest to the user. 
2. Detect a CSP-related warning issued by Chrome when launching. I think I heard that it was somehow possible.
3. A narrower solution for starters: just detect that it's an unfixed Polymer JS (when cloning, bower-installing, or opening from disk) and suggest a fix.

Did you mean any of these?