Changed start of week for Australia to Sunday as requested in https://code.djangoproject.com/ticket/21989
Merge pull request #2430 from NathanRSmith/ticket_21989

Fixed #21989 - Modified first day of week in AU locale.

Although Australia is a signatory to ISO 8601, there's a lot of evidence to suggest that this is in the same category as "officially, the USA uses metric". See the ticket for supporting details.