Fix geocoding error code

[rabidllama]

Pull Request Checklist

• 1. I have merged the latest version of the development branch into my feature branch and all conflicts have been resolved
• 2. I have added information about the change/addition to functionality to the CHANGELOG.md file under the [Unreleased] heading
• 3. I have documented my code using JDocs tags
• 4. I have removed unecessary commented out code, imports and System.out.println statements

- [ ] 5. I have written JUnit tests for any new methods/classes and ensured that they pass

• 6. I have created API tests for any new functionality exposed to the API

- [ ] 7. If changes/additions are made to the app.config file, I have added these to the app.config.sample file along with a short description of what it is for, and documented this in the Pull Request (below)

• 8. I have built graphs with my code of the Heidelberg.osm.gz file and run the api-tests with all test passing
• 9. I have referenced the Issue Number in the Pull Request (if the changes were from an issue)

- [ ] 10. For new features involving building of graphs, I have tested on a larger dataset (at least Germany) and the graphs build without problems (i.e. no out-of-memory errors)

• 11. I have written in the Pull Request information about the changes made including their intended usage and why the change was needed.

Fixes #113 .

Information about the changes

• Key functionality added: Geocoder now returns a 404 error rather than 200 code if no location was found from a reverse geocode lookup
• Reason for change: Issue Geocoding returns HTTP 200 on unknown location #113

Required changes to app.config (if applicable)

• None

[rabidllama]

@TheGreatRefrigerator - can you check that this won't cause issues on the front end with ajax handling?