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
[] means "see whether if it can be omitted or not":

[In much ]the same way [that ]a Django model describes the logical structure of an object, its behavior, [and ]the way its parts are represented[ to us], and determines how it's handled by the database, ...