Uglify first then bundle

- [x] @Attamusc (please see https://github.com/behance/be.net/pull/7769/files for the use of the new tasks)

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High-level flow:

* Clean out `public/assets-built` and `public/assets-ugly` (new folder)
 * This won't be necessary with lazy uglification (when we keep the uglified assets between runs)
* Copy `css` and `templates` folders from `public/assets` into `public/assets-ugly`
 * Need this so that r.js can resolve templates and css requires
* Uglify all js files from `public/assets/js` into `public/assets-ugly/js`
* r.js apps from `public/assets-ugly` into `public/assets-built`
* Swap

- [x] requires bump of grunt-be-ugly after merge of https://github.com/behance/grunt-be-ugly/pull/2