Import is inconsistent with edit and api

[sol1-matt]

The import is inconsistent with editing and the api

• you can't import the site, but you can import the location
• assignment in the api is via device or module, assignment in the import is via hardware type, manufacture and model

could be more, needs checking and tidy up

[sol1-matt]

this is on the asset model

[sol1-matt]

hardware_kind, manufacturer and model_name are used in import over the default fields module_type, device_type, inventoryitem_type and rack_type because using 4 separate fields would require conditional required fields which a) might not be possible and b) would be confusing for users.