Issue #2050759 by tim.plunkett, fietserwin: Move drupal_chmod and other code in file.inc to a Drupal\Core\File\FileSystem class

Revert "Issue #2388749 by alexpott, adci_contributor, ParisLiakos: Register symfony's mime guessers if they are supported"

This reverts commit 4dae1d99.

Issue #2388749 by alexpott, adci_contributor, ParisLiakos: Register symfony's mime guessers if they are supported

Issue #2387443 by alexpott, dawehner: BinaryFileResponse can fail because the core MIME guessing is not added to the MimeType singleton

Issue #1921558 by ParisLiakos, xjm, Dave Reid: Convert file_get_mimetype() to use Symfony MimeTypeGuessers.

Issue #1468328 by Berdir: Move file entity info, managed file, and file usage functionality into File module.

Issue #1668820 by sun, xjm, tim.plunkett, fgm: Concept, base class, and interface for configurable objects.

Issue #1615236 by Berdir, aspilicious: Merge entity controller interfaces, document and add default entity class definition.