WIP cleanup bugs with shift exchanges, list changes and codes
- Fix backup as 'is_active=False' added filters when looking for it,
- Fixed broken tests,
- Fake model to mock shift for buffers,
- Shift change notification on date/slot different than on member (new email template)
- Closes #124 (closed) #112 #121 (closed) #114
- Closes #125 (closed) (align some UI elements)
- Closes #115 (closed)