Improve touchscreen support on desktop platforms

[peppy]

Currently clicks are being handled incorrectly, and generally support doesn't exist.

Check out https://blogs.msdn.microsoft.com/dotnet/2017/04/05/announcing-the-net-framework-4-7/ (search WPF Touch/Stylus support for Windows 10) for a potential good starting point for better windows touch handling.

[FreezyLemon]

This looks really nice, but is probably not usable in osu-Framework since all the required classes are in PresentationCore.dll which is the WPF "core" module (example 1, 2).
I'm not sure whether adding this as a dependency is wanted.. though just as a reference, I'll mention that the file is ~1.3MB in size.

We might be able to implement this at a lower level in Windows (look at example 2, especially the FrameReported event, there are strong hints at it just being a native win API function call) without needing those classes though.

[peppy]

That was never said, no. It is just pending behind hundreds of other tasks that also need to be completed. Please have some patience.

[VPeruS]

WPF will be available in netcore3.0 but only for Windows

[frenzibyte]

Seems to be a high priority for touchscreen users.