usb_cam: 0.1.8-0 in 'groovy/distribution.yaml' [bloom]

Increasing version of package(s) in repository `usb_cam` to `0.1.8-0`:

- upstream repository: https://github.com/bosch-ros-pkg/usb_cam.git
- release repository: https://github.com/bosch-ros-pkg-release/usb_cam-release.git
- distro file: `groovy/distribution.yaml`
- bloom version: `0.5.11`
- previous version for package: `0.1.7-0`

## usb_cam

```
* autoexposure and exposure settings now exposed via ROS parameters
* added ability to call v4l-utils as well as correctly set autofocus
* cleanup of output
* Merge pull request #15 from mistoll/develop
  added support for RGB24 pixel format
* Added RGB24 as pixel format
* Contributors: Michael Stoll, Russell Toris
```