UPGRADE: Removed gridfield add new variation button

git-svn-id: https://silverstripe-ecommerce.googlecode.com/svn/modules/ecommerce_product_variation/trunk@4616 950b781c-c544-efab-2f99-90083ee69683
UPGRADE: to 3.1

git-svn-id: https://silverstripe-ecommerce.googlecode.com/svn/modules/ecommerce_product_variation/trunk@4617 950b781c-c544-efab-2f99-90083ee69683