Issue #2378095 by Wim Leers, Devin Carlson: Convert all remaining attached individual CSS/JS assets to attached asset libraries

git commit -m 'Issue #2377397 by Wim Leers, alexpott: Themes should use libraries, not individual stylesheets'

Issue #1510544 by swentel, Bojhan, Gábor Hojtsy, merlinofchaos, Cottser, Wim Leers, plopesc, aspilicious, sannejanssen,  larowlan, tim.plunkett, nod_: Fixed Show previews in front-end theme, able to select different view modes.

Issue #2138073 by damiankloip, xjm: Remove module_load_include() call from NodeController::revisionOverview().

Issue #1996238 by sun, nod_, damiankloip, Wim Leers, longwave, alexpott, Xano, mdrummond, Mark Carver, Jeff Burnz, highrockmedia, joelpittet, et al: Replace hook_library_info() by *.libraries.yml file.