Disable browser caching for guest files

Guests were getting confused because they'd upload a new bio pic but when they downloaded it, they'd get the old one. It seems like this was an issue on the browser side, so we now instruct browsers to not cache the page handlers that serve these files.

uber/site_sections/guests.py

@@ -605,12 +605,14 @@ def view_inventory_file(self, session, id, item_id, name):
                     cherrypy.response.headers['Accept-Ranges'] = 'bytes'
                     cherrypy.response.headers['Content-Length'] = filesize
                     cherrypy.response.headers['Content-Range'] = 'bytes 0-{}'.format(filesize)
+                    cherrypy.response.headers['Cache-Control'] = 'no-store'
                     return serve_file(filepath, disposition='inline', name=download_filename, content_type=content_type)
                 else:
                     raise cherrypy.HTTPError(404, "File not found")
 
     def view_bio_pic(self, session, id):
         guest = session.guest_group(id)
+        cherrypy.response.headers['Cache-Control'] = 'no-store'
         return serve_file(
             guest.bio.pic_fpath,
             disposition="attachment",
@@ -619,6 +621,7 @@ def view_bio_pic(self, session, id):
 
     def view_stage_plot(self, session, id):
         guest = session.guest_group(id)
+        cherrypy.response.headers['Cache-Control'] = 'no-store'
         return serve_file(
             guest.stage_plot.fpath,
             disposition="attachment",