Issue #2226323 by kpv | danylevskyi: Fixed CompositeFormElementTrait causes identical HTML ids for element and its wrapper.
Issue #2349605 by larowlan: Fixed EntityReferenceItem is fragile about entity save order.
Issue #2350941 by rpayanm | dawehner: Simplify $language max weight code using max().
Issue #1434670 by AlPotapov, bleen18 | ericduran: Add test for verticle_tabs default.
Issue #2353823 by ultimike: D6->D8 Migration missing variable: cache.
Issue #2352385 by andypost: Standardize book & forum entity route names.
Issue #2354177 by yched: Shortcut::getRouteParams() should be named getRouteParameters() for consistency.