[1.6.x] Added 1.6.1 release date.
[1.6.x] Post release version bump.
[1.6.x] Removed weird unicode char in some de po files

Refs #21601.
[1.6.x] Added 1.6.2 release notes stub.

Backport of ccd80dc3b6 from master
[1.6.x] Fixed #21580 -- Clarified why render() does not return a TemplateResponse object.

Backport of f685f94c98 from master
[1.6.x] Fixed link text for "Testing in Django" in tutorial 5.

Backport of e1cfc4b96a from master
[1.6.x] Fixed #21614 -- improved docs on configuring email for development.

Backport of d599b590eb from master
[1.6.x] Fixed #21539 -- Added example of modelformset_factory's form argument

Backport of 1fa681ee11 from master
[1.6.x] Added internal link to i18n documentation.

Backport of e904d421d06bb53fbc9f55bd129b0b213d9908c5 from master.
[1.6.x] Fixed typo in docs/ref/models/fields.txt

Backport of dfc95d240d from master.
[1.6.x] Added some internal links to render_to_string documentation.

Backport of 1689744aee1f13b2f4e270ce63cea143eb6d868e from master.
[1.6.x] Fixed #21625 -- incorrect documentation for DiscoverRunner.build_suite

Backport of b62031441b2e1cb1eeb7e1d6f254c553643add96 from master.
[1.6.x] Fixed #21632 -- Docs: Removed example with callable as query parameter

Using callables as query parameters is undocumented and not working,
so this changes an example from the ForeignKey.limit_choices_to
documentation that uses it.

Backport of d34c8c338a from master
[1.6.x] Fixed #21613 -- Removed a hardcoded input id from the tutorial.

Thanks Bruno Brouard for the report.

Backport of cc2d960274 from master
[1.6.x] Fixed #21585 -- Updated some links to 3rd party database projects.

Thanks graeme.perrow at sap.com for the original report.

Backport of 23d9f517dc from master
[1.6.x] Fixed #21213 -- Added docs for Django's mailing lists.

Added docs/internals/mailing-lists.txt documenting the use of django's
mailing lists. All references across docs changed to point to this page.

The referencing makes use of substitution because there's no way to make
a :ref: link in a non-inline fashion in Sphinx. It also makes use of
rst_epilog Sphinx conf for making this substitutions across all the
docs.

Backport of 3895d8899d from master
[1.6.x] Fixed #21663 -- Added missing WSGIPythonPath in mod_wsgi config.

Thanks carrie.hazelton at altamiracorp.com for the report.

Backport of e82e7ae1e8 from master
[1.6.x] Fixed #21662 -- Kept parent reference in prepared geometry

Thanks Robert Scott for the report.
Backport of 542198c1d0 from master.
[1.6.x] Fixed #21627 -- Added unicode_literals to changepassword command.

Fixed a crash when executing changepassword command when the user object
representation contained non-ASCII characters.

Backport of 398642fd9b from master
[1.6.x] Fixed typo and slightly improved error message when db is missing time zone definitions.

Refs #21432.

Backport of 32e75803be from master