Allow Foresee assets to be hosted

Rather than create another directory here (Eg, common/app/public/vendor/..) I've put all
these files inside the javascripts directory because it is a *javascript* application with
some asset dependencies. Ie. The entry point to these files is,

 common/app/assets/javascripts/modules/analytics/foresee-survey.js
Split the vendor & javascript copy tasks
Merge pull request #3588 from guardian/foresee-assets

Foresee assets