Change how organization entries are stored

[genericFJS]

There was a problem for organization items: If the item had a folder, the items would appear in the groups outside of the organization. Additionally, no folders were created in the organization.

This PR fixes that and changes how the entries are stored in the organization. Each organization has a sub-group for folders and collections. For items which have a group, the respective group is created in the folders group of the organization. The collections are added as groups to the collection group.

This resembles the structure how it is presented in vaultwarden.

[genericFJS]

Additionally a nested/flat mode is added, so one can decide if the backup should be better browseable with keepass groups for folders/collections of organizations or better searchable without duplicate entries.