Merge branch 'release/v3.1.41' into develop
Update data-merge documentation.
Update bibref/biblio.js

added "sticky" reference for HTML5 CR
Add support for 'scheme' config variable: if defined, loads external resources using the defined scheme instead of the scheme acquired via location.protocol. Values 'http' and 'https' are supported.
Update js/w3c/headers.js

Added alt-format class to alternate format links
Fix broken ABC ref.
Biblio: Update CS-ADAPTATION.
Biblio: update CSS21.
Biblio: update CSS-BG.
Biblio: update CSS-MEDIAQUERIES.
Biblio: update CSS3VAL.
Biblio: update SELECT.
Biblio: Update CSS3-IMAGES.
Biblio: Note to self: don't make titles up. :(
Biblio: Update FLEXBOX ref.
Biblio: update CSS3-TRANSFORMS.
Biblio: update CSS3-FONTS.
Biblio: update WOFF.
Biblio: update CSS3TEXT.
Biblio: update CSS3-ANIMATIONS.