Update builds tools version to 15

BuildTools/BuildControls.UWP.proj

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" ToolsVersion="12.0">
+<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" ToolsVersion="15.0">
 
   <Import Project="$(MSBuildProjectDirectory)\Config.UWP.proj" />