Removed stale add_q() comment
Fixed #20988 -- Added model meta option select_on_save

The option can be used to force pre 1.6 style SELECT on save behaviour.
This is needed in case the database returns zero updated rows even if
there is a matching row in the DB. One such case is PostgreSQL update
trigger that returns NULL.

Reviewed by Tim Graham.

Refs #16649
Improved {% include %} implementation

Merged BaseIncludeNode, ConstantIncludeNode and Include node.

This avoids raising TemplateDoesNotExist at parsing time, allows recursion
when passing a literal template name, and should make TEMPLATE_DEBUG behavior
consistant.

Thanks loic84 for help with the tests.

Fixed #3544, fixed #12064, fixed #16147
Set 'bidi' Urdu property to True

Refs #20454.
Fixed #20989 -- Removed useless explicit list comprehensions.
Fixed #21005 -- Made schema tests language-independent

Thanks Simon Charette for the review.
Fixed #20999 - Allow overriding formfield class with choices, without subclass restrictions.

Refs #18162. Thanks claudep and mjtamlyn for review.
Fixed typo in docs/ref/models/options.txt
Fixed copy/paste error in measurement docs
Make cache tag try to use "template_fragments" cache, if available.
Allow specifying caching backend for cache tag
Use compile_filter not Variable for using argument
Avoid creating extra connections to default cache
Add defaultdict to context to avoid creating multiple instances of a cache for the cache tag