add a note about "get_foo_display" in template documentation

It's used the same way as every other function: just write out its name and be sure to leave off the parentheses ;)

On a serious note, though, I think what would be more appropriate is a "how do I take this handy function and use it in a template" section which really explains this; just picking out specific functions and saying "to use function X, do Y" could give people the impression that those are the _only_ functions you're allowed to use.

Yes, I agree we need a section in the template documentation about the fields that provide these additional functions, with a short note about how they are used. Most are mentioned on the model api page, but that is not where a template designer will be looking. Perhaps these functions should instead be listed on the template documentation page and linked to from the field sections on the model api page.

I think it's not unreasonable to point template authors to the model docs when they're dealing with models in the template. I'm gonna WONTFIX this one.