Revert "According to http://blogs.msdn.com/b/vcblog/archive/2011/03/11/10140139.aspx signing is pretty broken in VS2010. Going to use a custom build step to do the signing as I don't fancy editing the installed MSBuild on the build agents"

This reverts commit baa682708bd727618b77e3b4ebd923f2942a456c.