[1.4.x] Fixed #20665 -- Missing backslash in sitemaps documentation

Backport of 5005303ae7919eef26dab9f8ba279696966ebf1d from master.
[1.4.x] Fixed #18944 -- Documented PasswordResetForm's from_email argument as a backwards incompatible change for 1.3

Thanks DrMeers for the report.

Backport of dab921751d from master
[1.4.x] Fixed #19196 -- Added test/requirements

Backport of 4d92a0bd86 from master
[1.4.x] Fixed #20730 -- Fixed "Programmatically creating permissions" error.

Thanks glarrain for the report.

Backport of 684a606a4e from master
[1.4.x] Fixed #20756 -- Typo in uWSGI docs.

Backport of a3242dc9fe from master
[1.4.x] Atom specification URL updated

Changed to the URL of the official RFC for Atom, since Atomenabled.org
is just a holding page.

Backport of beefc97171 from master
[1.4.x] Fixed #20792 -- Corrected DISALLOWED_USER_AGENTS docs.

Thanks simonb for the report.

Backport of dab52d99fc from master
[1.4.x] Fixed #18315 -- Documented QueryDict.popitem and QueryDict.pop

Thanks gcbirzan for the report.

Backport of 8c9240222f from master
[1.4.x] Fixed #20779 -- Documented AdminSite.app_index_template; refs #8498.

Thanks CollinAnderson for the report.

Backport of 7de35a9ef3 from master
[1.4.x] Added a bugfix in docutils 0.11 -- docs will now build properly.

Backport of a3a59a3197 from master