get_results is missing flow_rate when getting pump data

```
pump_names <- inp$pumps$Name

data_pumps <- kwb.swmm::get_results("00_template.out", 
                                    type = "links", 
                                    object_name = pump_names)
```

Here only the pump parameters **average_water_depth**, **flow_velocity**, **volume_of_water** and **capacity** gets loaded. 

The parameter **FLOW_RATE** of pump is missing.
