Use a CDN for third-party dependencies

[mgeisler]

Investigate loading JS files fromhttps://developers.google.com/speed/libraries/, http://www.jsdelivr.com/ or https://cdnjs.com/. If necessary, we may upload the missing libraries ourselves.

[mgeisler]

I think we'll instead just minify the JS and CSS code as needed. This avoids third-party dependencies and should be faster when the application is loaded with an empty cache.