Document django.template.add_to_builtins() or provide a standard way to add template tags from view code

[anatoly techtonik <techtonik@…>]

​https://docs.djangoproject.com/en/dev/howto/custom-template-tags/

Currently, you need an obligatory {% load %} tag in all you templates if you want to use custom application tags. That's inconvenient. There is a django.template.add_to_builtins() function that accepts a string argument - a module name, which solves the problem. But this function is:

1. Undocumented
2. Module name is not convenient

I propose the following mechanism:

from codereview import customtags

django.template.add_library(customtags, default=True)

[Ramiro Morales]

Duplicate of #17085. Seem like it isn't worth pushing things in this path, but rather aim for the greater refactoring proposed in #17093.