[NPANDAY-580] attach XBAP files in build

When a project carries a WPF Browser Applocation, then set a flag so
that the MSBuild plugin (which is used to generate the project) knows
to attach it to the build

git-svn-id: https://svn.apache.org/repos/asf/incubator/npanday/trunk@1453327 13f79535-47bb-0310-9956-ffa450edef68