Fixed #22796 -- Added more basic explanations of forms

Now explains some more basic form handling before discussing Django;
simplifies initial examples; defers explanation of more advanced
aspects until later in the document
Technically, they're not templates, at least by Django's parlance. Components/widgets perhaps, in the case of individual field renderings, or shortcuts in the case of the `as_{x}` form methods, but neither use the same mechanisms as `django.template`, which will be what users come to expect from the word `template` when working with Django.