Enable elevation interpolation of bridges and tunnels

[aoles]

Pull Request Checklist

• 1. I have rebased the latest version of the master 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 unnecessary 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 wiki page on github 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 or changes 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. For new features or changes involving the graphbuilding process (i.e. changing encoders, updating the importer etc.), I have generated longer distance routes for the affected profiles with different options (avoid features, max weight etc.) and compared these with the routes of the same parameters and start/end points generated from the current live ORS. If there are differences then the reasoning for these MUST be documented in the pull request.
• 12. I have written in the Pull Request information about the changes made including their intended usage and why the change was needed.

Fixes #685.

Information about the changes

• Key functionality added: elevation interpolation of bridges and tunnels.

• Reason for change: incorrect elevation of road structures due to use of ground surface elevation.

Examples and reasons for differences between live ORS routes and those generated from this pull request

• See Elevation Calculation Ignores Tunnel #685 (comment).

Required changes to app.config (if applicable)

• optional routing profile parameter interpolate_bridges_and_tunnels for toggling elevation interpolation on/off. When unset the default is to perform interpolation provided that elevation data is available.

[aoles]

This PR requires the updated GH version from GIScience/graphhopper#29 for the API tests to pass.

[takb]

looks good