* Updated all NuGet packages to latest, and updated the framework from .NET Core 3.0 to 3.1.
* Updating appveyor settings for 3.1
Updating appveyor to use the netcoreapp3.1 path instead of 3.0.
* Removing unneeded NuGet package System.Runtime.CompilerServices.Unsafe.
* Removing unused NuGet package SharpFontCore.
* Removing unused NuGet package TimeZoneConverter.Posix
* Cleaning up by adding newline to a csproj.
* Simplfying a NuGet conditional include, and adding a warning disable for an annoying NuGet package.
* I'm not sure if .travis.yml is still used, but I'm updating its 'dotnet' version to the correct SDK.
* Making the runtime version into its own environment variable so it's a bit easier to change in the future.
* Removing OpenTK.NetStandard reference from Ryujinx.Common
* Fixing indentation in Common.csproj
* Updating the README to specify .NET Core 3.1.
* Reverting the update of the GTKSharp package so it doesn't block the PR.
Support shared color masks (used by Nouveau and maybe the NVIDIA
driver).
Support draw buffers (also required by OpenGL).
Support viewport transform disable (disabled for now as it breaks some
games).
Fix instanced rendering draw being ignored for multi draw.
Fix IADD and IADD3 immediate shader encodings, that was not matching
some ops.
Implement FFMA32I shader instruction.
Implement IMAD shader instruction.
