hector_models: 0.3.1-0 in 'hydro/distribution.yaml' [bloom]

Increasing version of package(s) in repository `hector_models` to `0.3.1-0`:

- distro file: `hydro/distribution.yaml`
- bloom version: `0.5.2`
- previous version for package: `0.3.0-0`

## hector_components_description

```
* Re-parent LIDAR and camera mount to top_box_link
* Add xacro macros for setting dimensions
* Remove obsolete files
* Add UTM-30LX macro to vision box xacro
* Add hector ugv vision box to hector_components_description package for better reusability
* Contributors: Stefan Kohlbrecher
```

## hector_models

```
* made hector_models a true metapackage
* Moved package hector_sensors_gazebo to ../hector_gazebo
* Contributors: Johannes Meyer
```

## hector_sensors_description

```
* added hokuyo_utm30lx_model and hokuyo_utm30lx_gpu macros and disabled gpu laser in default hokuyo_utm30lx macro
* use gpu_ray sensor in hydro
* Contributors: Johannes Meyer
```

## hector_xacro_tools

- No changes