Angular v1.2.20 support, closes item:783

Manually enable Angular CSP mode as auto-detection triggers a harmless, though
nonetheless annoying CSP error.

CSP detection has also proved to be brittle.

Override Angular's Bower main block to include `angular-csp.css` so that Wiredep
can inject it for us.

See: https://github.com/angular/angular.js/pull/8191
Merge pull request #493 from tlvince/refactor/angular-manual-csp

Angular v1.2.20 support, closes item:783