Switch our default VisualStudioVersion to 14.0

This only takes effect if you're building in a versionless command
prompt.

build/Targets/VSL.Settings.targets

@@ -3,6 +3,10 @@
   <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props"
           Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props') AND '$(MSBuildProjectExtension)' != '.vcxproj'" />
 
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0</VisualStudioVersion>
+  </PropertyGroup>
+
   <PropertyGroup Condition="'$(DevEnvDir)' == ''">
     <DevEnvDir>$(VSINSTALLDIR)\Common7\IDE</DevEnvDir>
     <DevEnvDir Condition="'$(VisualStudioVersion)' == '12.0'">$(VS120COMNTOOLS)\..\IDE</DevEnvDir>
@@ -11,7 +15,6 @@
   </PropertyGroup>
 
   <PropertyGroup>
-    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">12.0</VisualStudioVersion>
     <VisualStudioReferenceMajorVersion Condition="'$(VisualStudioReferenceMajorVersion)' == ''">$(VisualStudioVersion.Substring(0, $(VisualStudioVersion.IndexOf('.'))))</VisualStudioReferenceMajorVersion>
     <VisualStudioReferenceAssemblyVersion Condition="'$(VisualStudioReferenceAssemblyVersion)' == ''">$(VisualStudioReferenceMajorVersion).0.0.0</VisualStudioReferenceAssemblyVersion>
     <VisualStudioCodename>Dev$(VisualStudioReferenceMajorVersion)</VisualStudioCodename>