qt_gui_core: 0.2.22-0 in 'indigo/distribution.yaml' [bloom]

Increasing version of package(s) in repository `qt_gui_core` to `0.2.22-0`:

- distro file: `indigo/distribution.yaml`
- bloom version: `0.5.1`
- previous version for package: `0.2.21-0`

## qt_gui_app

- No changes

## qt_gui_py_common

- No changes

## qt_gui_cpp

```
* add shutdown notification for plugin providers (#39 <https://github.com/ros-visualization/qt_gui_core/issues/39>)
```

## qt_gui

```
* add shutdown notification for plugin providers (#39 <https://github.com/ros-visualization/qt_gui_core/issues/39>)
```

## qt_dotgraph

- No changes