Version number included in ETag hash.
The REST API now includes the REST server's version number in the string that gets hashed and used as ETag. The version comes from the `<version>` tag in the pom.xml. It can also be accessed via HTTP at `/version`. The filename of the jar will also reflect the version number. This means we should start doing more proper releases of the REST API like we do with the Java API. Fixes #1853