Added Base.update_collection that can update an array of id/attribute pairs, such as the ones produced by the recent added support for automatic id-based indexing for lists of items #526 [Duane Johnson]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@496 5ecf4fe2-1ee6-0310-87b1-e25e094e27de