Add BulkImportHelper

```
    persistence                = BulkImport.new(data)
    institution.postal_address   = persistence.address
    institution.locations        = persistence.locations
    institution.contact_officers = persistence.contact_officers
```
vs
```
    institution.postal_address   = BulkImport::address(data['postal_address'])
    institution.locations        = BulkImport::address(data['locations'])
    institution.contact_officers = BulkImport::address(data['contact_officers'])
```