Bower: add ot.js and scratchpad to the dependencies
App: embed a ScratchArea into rooms
App: bundle prompts for video and audio
Fix ScratchArea closing and error
Remove the Etherpad widget

Now a similar feature is handle by ScratchPad.
Check https://github.com/tOkeshu/scratchpad for more infos
Merge branch 'feature/scratchpad'