Platform configuration refactoring

[kekekeks]

Right now if one wants to change initialization options for a particular platform, it's needed to explicitly initialize it with UseXXX method on app builder. Options are passed using positional arguments. This approach has two issues:

1. UsePlatformDetect can't be used anymore
2. ABI compatibility is broken when new parameters are added

What I think we should do instead is to register options for a particular platform in app builder before calling platform detect. E. g.:

AppBuilder.Configure<App>()
      .With(new Win32Options { UseEgl = true, UseDeferredRenderer = false }
      .With(new MacOptions { ShowInDock = false })
      .UsePlatformDetect();