Remove plugin URL from dev JS files, and get grunt build-prod to add it back on a prod build
Remove plugin URL banner from all LESS files
Regenerated src CSS files for dev

The recent changes to move the banner generation only into prod files
means a few commits like these to straighten things up.
Grunt CSSJanus doesn't have a banner option, so remove that config.
Grunt CSSMin: add Achievements URL to top of all CSS in prod builds