Removed Vietnamese resource file due to its age, probable low demand and because it has fewer than 25% (440 still-used strings out of 1900) of the strings translated. It can be resurrected if someone wants to substantively complete it.

git-svn-id: https://svn.apache.org/repos/asf/roller/trunk@1606971 13f79535-47bb-0310-9956-ffa450edef68