[1.0.X] Did some much-needed rewriting/editing in the formsets section of...

[1.0.X] Did some much-needed rewriting/editing in the formsets section of docs/topics/forms/modelsforms.txt. 'It self' is not two words. Backport of [9616]

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@9617 bcc190cf-cafb-0310-a4f2-bffc1f526a37