moved project.save_as_excel to the model level, just moved, no function yet.
change foreign_key between projects and forums to project_id instead of year
moved save_as_excel to forum model, since it saves all projects and associated data of one forum. (as Excel in Dropbox) Problem currently is the associated data like Project.schools_csv
fixed pupils_csv and schools_csv in project model
removed save_in_dropbox from projects_controller, since it is now a methode in Forum
change Forum.current.save_as_excel to project.forum.save_as_excel in projects_controller