[1.5.x] Avoided a possible regression in 5097d3c5.

QuerySet.none() returns an instance of EmptyQuerySet, which may have
undesirable side effects in the presence of custom query set classes.

The implementation of .none() was refactored in master to have the same
effect as .filter(pk__in=[]).

Refs #19652.

Thanks Simon Charrette for the report.
[1.5.x] Fixed #19639 - Updated contributing to reflect model choices best practices.

Thanks charettes.

Backport of eaa716a413 from master
[1.5.x] Fixed #19577 - Added HTML escaping to admin examples.

Thanks foo@ for the report and Florian Apolloner for the review.

Backport of eafc036476 from master
[1.5.x] Fixed #19665 -- Ensured proper stderr output for Command.run_from_argv

Thanks Stefan Koegl for the report and Simon Charette for the review.
Backport of b9c8bbf37 from master.
[1.5.x] Added more shortcuts to i18n docs in index page.

5b99d5a from master
[1.5.x] Fixed a malformed link.
[1.5.x] Fixed #19683 - Added a missing import in signing example.

Thanks sunsongxp@ for the report.

Backport of 537d44b1b9 from master
[1.5.x] Fixed typos in docs and comments

Backport of ee26797cff from master
[1.5.x] Fixed #19076 -- Added content_type attribute to TemplateView.

Thanks Gavin Wahl.

Backport of 23e319d.
Added file forgotten in d5ad9d3d.
[1.5.x] Fixed #19692 -- Completed deprecation of mimetype in favor of content_type.

Thanks Tim for the report and initial patch.

Backport of 89cb771 from master.
Enhanced traanslator comments documentation.

Partial (docs only) backport of 47ddd6a from master.
[1.5.x] Fixed #19708 -- Exception in timezone.override(None).

Thanks rafales.

Backport of 9a4a1ce.
[1.5.x] Fixed #19714 -- Updated documentation about TemplateView context

Thanks Aramgutang for the report. Refs #17228.
Backport of 56e553129 from master.
[1.5.x] Documented ArchiveIndexView's date_list context variable.

Refs #16218.

Backport of a0c67c6.
[1.5.x] Fix rst syntax error.

Thanks Chris Rebert for the report.

Backport of d75a54c.
[1.5.x] Fixed #19690 - Removed unused import in doc examples.

Backport of c6560e4843 from master
[1.5.x] Fixed content types contrib app doc typos.

1ee40f2 from master.
[1.5.x] Small generic FK docs tweaks.

5f7eecd from master.
[1.5.x] Fixed #18144 -- Added backwards compatibility with old unsalted MD5 passwords

Thanks apreobrazhensky at gmail.com for the report.
Backport of 63d6a50dd from master.