* Changed default sound/display methods to OpenAL/OpenGL on Windows to match
non-Windows, and replaced DirectInput with OpenTK input (needs regression
testing on Windows).
* (meta) As a result of the above, DirectX is no longer a prerequisite, leaving
only: .NET Framework 4.6.1 (comes with Win10, as does 4.8), MSVC 14 (also comes
with Win10), MSVC 12 for Mupen, and MSVC 10 for BSNES/Mupen.
* Refactored static Program ctor, using ExceptionBox for missing prereqs, and
removed PrereqsAlert.
* Added OS version check for Windows, with a flag in the config to skip it.
* Updated readme for Win7 EOL (and generally cleanup Windows sections).
YoshiRulz