WIP: session cleanup
Make Collection's image_store required, as it's used by attachment upload
Merge branch 'session-cleanup'

* session-cleanup:
  Make Collection's image_store required, as it's used by attachment upload
  WIP: session cleanup
Merge branch 'master' of github.com:SlideAtlas/SlideAtlas-Server

Standard merge
Progress made on iPad textwidget positioning bug
Fixed conflicts