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

Issue #2384675 by sidharrell, cilefen, Mile23, damiankloip, dawehner, Wim Leers, alexpott, neclimdul: Deprecate conf_path()

Issue #2328111 by dawehner, martin107, neclimdul: Replace most instances of the DRUPAL_ROOT constant with the app.root container parameter.