Adds popup mode to 'my-thing-picker'

Example usage 

```html
<my-thing-picker
            data-model="model.dependencies.provides"
            data-allow-rm="true"
            data-thing-name="Service"
            data-list-inline="true"
            data-popup-mode="true"
          >
          </my-thing-picker>
```


what's this class for?