Ditch google cdn and add swiping to colorbox theme

I did these mainly for my own installation, but I think these can be useful for the upstream version, too:

bdef57a makes serving of the css and js files by google optional, increasing security and privacy (plus this has benefits for galleries, which are not served by an webserver)
c70900c adds swiping to the colorbox theme (colorbox does not support this out of the box), which is handy if you're watching the images on your mobile device