Added example of using sitemaps with static views.

References #16829.
Make Urdu (ur) recognized as RTL language. Refs #20454
Merge pull request #1142 from Pike/master

Fixed #20454: Make Urdu (ur) recognized as RTL language
Improve cookie based session backend docs.

Note the don't require sessions to be in installed apps.
Fix a typo in a comment.
Fixed #20452 -- Rename 'headers' to 'header fields'.
Added TransRealMixin to fix i18n global state pollution in the test suite
Merge pull request #1147 from ambv/transrealmixin

Added TransRealMixin to fix i18n global state pollution in the test suite
Fixed a rest mistake I introduced in d5ce2ff.
Merge pull request #1098 from zsiciarz/ticket-16829

Added example of using sitemaps with static views.
Fixed #12674 -- provide a way to override admin validation

Moved admin validation code to classes and have those be class
attributes to the ModelAdmin classes.
Fixed some line wrapping, refs #20233
Fixed #20429 -- added create_or_update

Added implementation for create_or_updated method on QuerySet.
Made changes required by @freakboy3742