Gyration: documentation

(cherry picked from commit d523213f648d6a10307932022c5aaba1fa93def4)
Some fixes in doc

(backported from 2.1)
Fixed changelog for 2.0.4
Version tag (2.0.4)
Typo
Merge remote-tracking branch 'origin/v2.0' into v2.0
Merge branch 'v2.0' into v2.0-hrex