code: func (mc MongoClient) AddValueDescriptor(v contract.ValueDescriptor) (string, error) {
  	s := mc.getSessionCopy()
  	defer s.Close()
  
  	var mapped models.ValueDescriptor
  	id, err := mapped.FromContract(v)
  	if err != nil {
  		return "", err
  	}
  
  	// See if the name is unique and add the value descriptors
  	found, err := s.DB(mc.database.Name).C(db.ValueDescriptorCollection).Find(bson.M{"name": mapped.Name}).Count()
  	if err != nil {
  		return "", errorMap(err)
  	}
  	// Duplicate name
  	if found > 0 {
  		return "", db.ErrNotUnique
  	}
  
  	mapped.Modified = db.MakeTimestamp()
  	mapped.Created = mapped.Modified
  
  	if err = s.DB(mc.database.Name).C(db.ValueDescriptorCollection).Insert(mapped); err != nil {
  		return "", errorMap(err)
  	}
  	return id, nil
  }
docs: // ************************* VALUE DESCRIPTORS *****************************
  // Add a value descriptor
  // 409 - Formatting is bad or it is not unique
  // 503 - Unexpected
  // TODO: Check for valid printf formatting