[change] Rethink LOCI_FLOORPLAN_STORAGE

[nemesifier]

Maybe it's overkill to have a dedicated storage class for django-loci, we could investigate whether we can default to the global storage class.

I believe the purpose of the custom storage class was to:

• delete the floorplan files when floorplan objects are deleted
• ensure uploading a new floorplan overwrites the current floorplan successfully