Release note anchors

[msuchane]

It's convenient when every release note has a HTML anchor attached to its heading. That way, you can link a specific release note in the document.

Add IDs to release note labels. Make sure that the IDs are unique, for cases where a release note is reused several times in the document.

[msuchane]

Currently, each release note does have an anchor, but the IDs aren't unique across the whole document. If a release note is reused, it results in an AsciiDoc ID error.

A solution is to track context variables in assemblies and modules, and add them to the RN IDs.