Setup DesktopGL project

[harry-cpp]

Notes:

• Restored the csproj ignore to .gitignore, we should force csproj files until move is done
• Added DesktopGL project
  • This targets both .netstandard2.0 and .net451, and this means that the nuget will be referencable by older projects as well
• Project file is a nuget package file at the same time :)
• I'm cheating because this isn't connected to the build bot, and is not breaking any stuff as our project name was never .DesktopGL.csproj

How to build nuget:

dotnet restore MonoGame.Framework/MonoGame.Framework.DesktopGL.csproj
msbuild /t:Pack /p:Version=3.8.0.3 MonoGame.Framework/MonoGame.Framework.DesktopGL.csproj

CC. @Jjagg

[mrhelmut]

net4 would be cool to have a compatibility toward WinXP, though it's not a big deal considering that Steam has stopped supporting it.
If it's holding anything back to move forward, let's just bid farewell to Net4.0 and WinXP (it has bad OpenGL drivers anyway).

[harry-cpp]

Yea, I actually need .NET 4.5.1 actually for corert stuff.

[mrhelmut]

So goodbye WinXP, that's a problem solved in some way. =P
Can't wait for a smoother CoreRT support!

[Jjagg]

Building nugets can be

dotnet restore MonoGame.Framework/MonoGame.Framework.DesktopGL.csproj
dotnet pack -p:Version=3.8.0.3 MonoGame.Framework/MonoGame.Framework.DesktopGL.csproj

[harry-cpp]

dotnet pack

That only works on Windows, on Mac/Linux you have to use msbuild to pack multitarget framework nugets. TLDR. dotnet msbuild does not support standard .net framework compilation on non Windows platforms.

[harry-cpp]

@Jjagg should be good now, one thing we forgot is Framework.Net.Platform projects are still in the same folder, we should move it to a separate folder.

[Jjagg]

URLs in props file are still yours.

Yeah, we don't have to do Net stuff in this PR.

[harry-cpp]

@Jjagg Yea, too many small mistakes to keep track of em. Hopefully no mistake now.

[Jjagg]

I tried building a game project created from the dotnet template with p2p reference to this csproj file and the MonoGamePlatform property didn't get set for my project (causing an error in MonoGame.Content.Builder).

EDIT: Maybe we should just add the property to the template directly? Anyway, that's not an issue with this PR.

[harry-cpp]

I tried building a game project created from the dotnet template with p2p reference to this csproj file and the MonoGamePlatform property didn't get set for my project (causing an error in MonoGame.Content.Builder).

EDIT: Maybe we should just add the property to the template directly? Anyway, that's not an issue with this PR.

Doesn't work like that, if you are not using nuget you have to manually set MonoGamePlatform property in your project if you wanna use MGCB targets, thats normal.

[Jjagg]

Okay, this is good to go. Merging! :D