Issue #2776975 by joelpittet, dawehner, tim.plunkett, xjm, pfrenssen: March 3, 2017: Convert core to array syntax coding standards for Drupal 8.3.x RC phase

Revert "Issue #2712647 by klausi, catch, slasher13, jibran, Manuel Garcia, alexpott, naveenvalecha, neclimdul, dawehner, Wim Leers, pounard: Update Symfony components to ~3.1"

This reverts commit a55b8ef1.

Issue #2712647 by klausi, catch, slasher13, jibran, Manuel Garcia, alexpott, naveenvalecha, neclimdul, dawehner, Wim Leers, pounard: Update Symfony components to ~3.1

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

Issue #2602872 by rakesh.gectcr: Wrong @param doc for construct function in class ContainerAwareEventDispatcher

Issue #1392754 by tss, justAChris, jhodgdon: Comply with new documentation standards for @file for namespaced class files