Issue #2575737 by Cottser, davidhernandez: Copy templates, CSS, and related assets to Stable and override core libraries' CSS

Issue #2031883 by mortendk, rachel_norfolk, andypost, zestagio, epari.siva, nguerrier, Manjit.Singh, rteijeiro, MathieuSpil, pablo.guerino, HOG, lauriii, LewisNyman, joelpittet, Wim Leers, Cottser, minneapolisdan: Markup for: comment.html.twig

Issue #2372909 by Tom Verhaeghe: Comments to check '$comment->getOwner->isAnonymous()' instead of assuming anonymous is ID 0

Issue #2329783 by lauriii, jamesquinton | davidhernandez: Move comment classes from preprocess to templates.

Issue #2271349 by Berdir, Arla, blueminds, larowlan, Dave Reid: Node and Comment ops links should be display components (which can be disabled).

Issue #2170251 by lauriii, mgifford, joshi.rohit100, lokapujya, mparker17, Mirabuck, Jalandhar: Fixed Comment headings can spit out empty heading tags.

Issue #2114563 by joelpittet, martin107, Cottser: Remove TwigReference with the help of 'without' filter replacing 'show'/'hide' functions.

Issue #731724 by larowlan, andypost, dixon_, tsvenson: Convert comment settings into a field to make them work with CMI and non-node entities.

Issue #1991684 by Wim Leers, rcaracaus, amateescu, msonnabaum: Fixed Node history markers (comment & node 'new' indicator, 'x new comments' links) forces render caching to be per user.

Issue #2013094 by pwieck, Cottser: Remove unnecessary template_preprocess() reference from all Twig files

Issue #1363112 by mparker17, mgifford, tlattimore, Jacine, dcmouyard, bowersox, ry5n, ahdiaz: Simplify names of 'element-x' helper classes.

Issue #1898054 by pixelmord, jenlampton, steveoliver, EVIIILJ, c4rl, vlad.dancer, Fabianx, joelpittet, jwilson3, thedavidmeister, shanethehat, Cottser: Convert comment module to Twig.