Fixed #10375 -- Added documentation about the default format strings used for...

Fixed #10375 -- Added documentation about the default format strings used for the `date` and `time` filters when no format string is passed to the filter, based on patch from kgrandis.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@10259 bcc190cf-cafb-0310-a4f2-bffc1f526a37