Issue #2317811 by ChandeepKhosa, emma.maria: Do not print the footer container in Seven when not in use.

Issue #1529814 by mgifford, JohnAlbin, ibullock, dcmouyard, mark.labrecque, andrewmacpherson, vegantriathlete: Fixed skiplink behavior for Webkit browsers.

Issue #2017257 by jason.bell, dead_arm, alexrayu, philipz, idebr, rteijeiro, emma.maria, frankbaele, LewisNyman: Create generic layout classes.

Revert "Issue #2218039 by sun, dawehner: Render the maintenance/install page like any other HTML page."

Broke update.php.

This reverts commit 10b03890.

Issue #2226185 by galooph, filijonka, Cottser: Remove @ingroup themeable from core theme Twig template docblocks.

Issue #1490402 by LewisNyman, nod_, mcjim, mdrummond, rteijeiro, jessebeach, Bojhan, ry5n: Redesign tabs and the content header.

Issue #1843650 by Mark Carver, jenlampton, Cottser: Remove the process layer (hook_process() and hook_process_HOOK).

Issue #2047061 by jessebeach: Fixed Remove redundant [role=navigation] in the header around the breadcrumbs in the Seven theme page template.

Issue #1589968 by cr0ss, Cottser, Pancho, DarthDrupal, Mark Carver: Move Title from process to preprocess, remove template_process_page().

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 #1932948 by falcon03: Primary tabs could not work in certain situations due to a wrong ARIA role.

Issue #1961870 by Cottser, foopang, kgoel, shanethehat, tlattimore, c4rl, joelpittet, thedavidmeister: Convert page.tpl.php to Twig.