[1.7.x] Fixed #23438 -- Added snippet & imports to docs/intro/overview.txt.

Backport of 88c4e01d34 from master
[1.7.x] Fixed #23340 -- Corrected naturaltime docs to match behavior.

Thanks zachborboa for the report and blackguest for the patch.

Backport of 7353e26d5d and 0a2bc6e6bd from master
[1.7.x] Fixed #22882 -- Fixed a UnicodeDecodeError in flush.

Thanks djbaldey for the report.

Backport of 0e4d79c4f0 from master
[1.7.x] Refs #23430 -- gunicorn wants a module, not file

Backport of fa74dba994 from master
[1.7.x] Fixed #23437 -- Documented required update of WSGI scripts for 1.7.

Thanks Tim for the review.

Backport of dfe209a from master
[1.7.x] Fixed #23416 -- Make sure DatabaseCreation respects checks.

Migrations respected Field.db_parameters()['check'], but
DatabaseCreation was still using just Field.db_type().

Backport of 14c8456 from master