Fixed #15918 -- Refined documentation of the various localization settings,...

Fixed #15918 -- Refined documentation of the various localization settings, especially with regard to the thousand separator. Thanks, Aymeric Augustin.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16727 bcc190cf-cafb-0310-a4f2-bffc1f526a37