event.html: added 'no file attached' message to the event screen, if no agenda file was uploaded for the event
event.html: added 'no file attached' message to the event screen, if no agenda file was uploaded for the event

clemens-huebner/amos-ss16-proj8,clemens-huebner/amos-ss16-proj8,clemens-huebner/amos-ss16-proj8