deleting entitites does not delete files

[klawr]

Describe the bug
When deleting an entity e.g. an Adresse the files attached to that entity are not moved to the trash.
They are left in the respective directory where the entity was before.

To Reproduce
Add file to entity and delete. It is not in the trash.

Expected behavior
Files should be moved to trash when deleting respective entity.

[klawr]

trash is now part of the entities in the backend.
Therefore it might be better to leave the files where they are.
Admins might get the possibility to detect zombie directories to clean them up