Full and proper support for high DPI

[FenPhoenix]

Right now, we just let Windows scale us as it sees fit, with the result that our UI looks slightly blurry when not at 100% scale, and I have reports that fonts may not be scaling quite as they should either. We might have to switch to .NET Framework 4.8 to do this, as judging from the release notes there's some high-DPI support improvements for WinForms in there that we might need. However, the requirements are the same as for 4.7.2, so it's not that much of a problem, other than making people download an entire new very large framework version that they may not have.

[FenPhoenix]

Reading about the goals for WinForms in .NET Core 3.0 ("Fix existing scaling bugs in Per Monitor DPI aware applications" and others), I'm going to wait for .NET Core 3.0's general release, then switch AL over. Till then, I'll hold tight with the imperfect scaling.