#386 Make cross-docset links to ESCET website version-specific

Made cross-docset links to ESCET website version-specific. E.g. one release notes page links to another for the same version.

Note that:

• Replacements happen during the Maven build. As such, looking at the AsciiDoc sources with any text editor, with the Eclipse AsciiDoctor Editor, or via the GitLab web GUI, the links won't work directly.
• I've made sure that the links work when built for a dev build, as well as for milestone/RC/final releases.
• I'ved tested this locally. We can test this out for real with v0.6-RC2.

Closes #386 (closed)