Saving an unkown resource should not respond 'success'

[ndoschek]

When trying to save an unknown resource, the model server responds with success:
{ "type": "success", "data": "Model 'file:/...' successfully saved" }

This is not correct, it should return an error, just like for example the DELETE endpoint.
{ "type": "error", "data": "Model 'file:/...' not found, cannot be deleted!" }