stack: rename stack.revs into stack.indexedrevs
They are accessible by an index, and are sorted. But they don't include all revisions for show in showstack().
This instance will be upgraded to Heptapod 0.20.1 on 2020-03-08 at 14:00 UTC+1 (10 minutes of downtime)
They are accessible by an index, and are sorted. But they don't include all revisions for show in showstack().