BUGFIX Correct locale mapping in DateField_View_JQuery for "en_US" and "en_NZ"
MINOR Fixed form validation message in DateField to include actual date format, rather than a hardcoded value
git-svn-id: svn://svn.silverstripe.com/silverstripe/open/modules/sapphire/branches/2.4@111843 467b73ca-7a2a-4603-9d3b-597d59a354a9