Finished sprint 1.

Added POST method to ItemController for UploadFile, this triggers when a
file is dropped into the dropzone on file submission question type.
Added a POST method to ItemController for DownloadAppendix, this
triggers when the download button is selected on appendix and is
currently hardcoded to download the 200x200.png image in ~/img folder.
bucketKey parameter is being successfully passed as the only requirement
needed to properly download the appendix from S3.
Added another image to ~/img.
Updated all of the styles on the changed _Shared views,