[1.8.x] Cosmetic edits and minor corrections to docs/ref/django-admin.txt.
[1.8.x] Cosmetic edits and minor corrections to docs/ref/django-admin.txt.

Backport of 99ec80f84a826b68cb7c09c662e411314f7c9b8c from master

h4r5h1t/django-hauthy,pquentin/django,h4r5h1t/django-hauthy,pquentin/django,pquentin/django,h4r5h1t/django-hauthy,h4r5h1t/django-hauthy