Allow local image build

- Remove dependency on github download
- Add `github/build.sh` for local builds
- Simplify gtaphhopper build
- Simplify handling of `graphhopper.sh` and `config-example.yml`

README.md

@@ -32,3 +32,5 @@ docker run --entrypoint /bin/bash israelhikingmap/graphhopper -c "wget https://d
 ```
 
 Checkout `graphhopper.sh` for more usage options such as import.
+
+In order to build the docker image locally, please run [`.github/build.sh`](.github/build.sh).