frontier_exploration: 0.1.8-0 in 'hydro/distribution.yaml' [bloom]

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

- distro file: `hydro/distribution.yaml`
- bloom version: `0.5.2`
- previous version for package: `0.1.4-0`

## frontier_exploration

```
* revert launch file to general form
* document helper functions
* Contributors: Paul Bovbel
```