Make file attachment upload work for event application forms

[cangoektas]

Exactly like in #27 we currently have a file upload for application forms which uses the image upload functions from the avatarFactory. Only this time it fails with the error:

failed: {"status":"error","errors":{"avatar":["Failed to manipulate with MiniMagick, maybe it is not an image? Original Error: `identify /var/folders/7b/5xf3r9tn4n7_q8qgz0mtrzd40000gn/T/mini_magick20160612-5654-18ydhfn.pdf` failed with error:\n"],"full_messages":["Avatar Failed to manipulate with MiniMagick, maybe it is not an image? Original Error: `identify /var/folders/7b/5xf3r9tn4n7_q8qgz0mtrzd40000gn/T/mini_magick20160612-5654-18ydhfn.pdf` failed with error:\n"]}}

Important files:

• form-participation-application.html
  • File select button defined pointing to the controller function cvFileSelected (done)
• participationCtrl
  • cvFileSelected function is where
  • the file upload function is called from the attachmentFactory (done)
  • where the status of the upload is updated for the view (done)
  • where the url of the uploaded file needs to be set as a property for the newly created application (TODO)
• attachmentFactory
  • uploadFile needs to specify attachment upload instead of avatar (TODO)

In order to test all this you need to

• Checkout to branch feature/events-file-uploads
• Go to localhost:9000/#/event
• Create new event (with application)
• Click on the event
• Click on Participate
• Select file for CV attachment

@ahmedissa hope you don't mind that I assigned you to this and #27