Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #2600672 by alexpott, dawehner: Core MarkupInterface implementations used in Twig templates should implement \Countable

Issue #2576533 by alexpott, stefan.r, Wim Leers, dawehner, xjm, effulgentsia, catch: Rename SafeStringInterface to MarkupInterface and move related classes

Issue #2568977 by alexpott, dawehner, pwolanin, Wim Leers: Replace SafeMarkup::format() in the link generator - it's a bad example to everyone

Issue #2335661 by Wim Leers, pwolanin, dawehner, Fabianx, larowlan, catch, Berdir: Outbound path & route processors must specify cacheability metadata