Allow {version} in the URLS for documentation and javadoc at admin/projects/{project}/releases

[rwinch]

Previously, we were able to use a variable {version} in the URLs for the documentation and Javadoc. This made updating the release version much easier. If combined with gh-1022 that would mean we could just change the version and save to perform a release.

[spencergibb]

It's what we use in spring cloud https://docs.spring.io/spring-cloud-commons/docs/{version}/reference/html/. It even replaces the latest GA release with current instead of a number.

[bclozel]

Thanks @spencergibb !
Indeed the {version} templated variable was working but this was not documented. I've pushed a change that pre-fills the documentation URLs with sensible defaults for most projects (using the project ID and the {version}) so this should make things easier.