VS: Re-arrange WriteExtraSource to support tool configuration

Add a code path to write the tool open and close elements separately
so that we can add content in between to configure it.
VS: Add a source file property to mark content for Windows App deployment

Create a VS_DEPLOYMENT_CONTENT source file property, supporting
generator expressions, to compute whether a source file should be marked
as DeploymentContent or ExcludedFromBuild in Windows Phone and Windows
Store projects.

Inspired-by: Minmin Gong <minmin.gong@gmail.com>
VS: Add a source file property to set the hlsl shader type

Create a VS_SHADER_TYPE source file property.

Inspired-by: Gilles Khouzam <gillesk@microsoft.com>
Merge topic 'vs-special-source-file-properties' into next

0c44cb94 VS: Add a source file property to set the hlsl shader type
08bfe04b VS: Add a source file property to mark content for Windows App deployment
0a2f1636 VS: Re-arrange WriteExtraSource to support tool configuration