Project cleanup

[burninrubber0]

Removes much of the deprecated, unused, or otherwise unnecessary clutter from the project. Most of this is .NET Framework-related and was carried over automatically (likely by try-convert).

• App.config files were used in .NET Framework. In .NET, they have been replaced by appsettings.json. Since the things app.config once referenced are gone, they have been deleted rather than replaced.
• AssemblyInfo.cs files are no longer necessary like they were in .NET Framework. They have been removed. The information they contained is now generated automatically.
• OpenTK.dll.config files are not needed on Windows and have been removed.
• Empty/unused Settings.settings and Resources.resx files (and their designer files) have been removed.
• <Compile /> items were needed in .NET Framework. They are no longer required in .NET and have been removed.
• All instances of <ImplicitUsings />, <Nullable />, <GenerateAssemblyInfo />, and <ImportWindowsDesktopTargets /> have been removed. The default will be used instead. These were mostly added automatically when the .NET migration occurred.
• <OutputType /> was added in projects that did not have it before.
• Three unused packages were removed from the main project.
• Various ClickOnce-related properties were removed from the main project.
• <StartupObject /> has been removed from the main project.
• App.manifest has been updated to run the application as administrator when possible. This partially addresses Warn if not running as admin #52, but there will still have to be a warning shown for users who cannot run applications as administrator.