Teach the VS 2015 generator to support WindowsStore 10.0 applications.
Add target properties to customize them:
* VS_WINDOWS_TARGET_PLATFORM_MIN_VERSION: Specifies the minimum version
of the OS that the project can target.
* VS_DESKTOP_EXTENSIONS_VERSION, VS_MOBILE_EXTENSIONS_VERSIONS,
VS_IOT_EXTENSIONS_VERSION: Add a reference to the version of the SDK
specified to the target allowing to target the extended functionality in
a universal project.
* VS_IOT_STARTUP_TASK: Specifies that the target should be
built as an IOT continuous background task.
* Add AppContainerApplication to non-UTILITY targets
* Generate app manifest and related files if project does not provide them.
Place them in a per-target directory to avoid clashes.
* Mark WinRT components with WinMDAssembly
* Import Windows Phone 8.0 targets in .vcxproj files when necessary,
and reference platform.winmd.
Inspired-by: Paul Annetts <paul@lightunobscured.com>
Gilles Khouzam