Feature.multifileupload

Without much further ado:

It's an integration of jquery-fileupload, allowing bulk file upload with multiple select or dnd. 
File sizes are visible and for images, a thumbnail is also seen before the upload is started. Progress bar is shown during the update.

Screencast: https://vimeo.com/98848252
Do all the JS support files (those not served as assets) belong in the `substanced` package at all (rather than in the root of the prjoect?)