Convert vsintegration projects to .NET Core SDK

[brettfo]

Eventually we'll properly use Directory.Build.props and Directory.Build.targets, but for the time being I don't want the non-SDK projects contaminated, so I opted to name everything FSharp.Directory.Build.props/.targets and opt-in each project by adding it's own Directory.Build.props/.targets next to the converted project files that redirects to the FSharp. ones.

To properly handle restoring <PackageReference /> items, NuGet.config had to be moved to the root of the repo so that it's always up-path from every project file.

Also, to enable overriding the F# SDK targets, the -proto suffix had to be removed. The proto compiler is still built into it's own directory, though, so there won't be any conflicts.

All projects under the vsintegration/ directory have been converted to the new SDK except the property pages because that was giving me no end of grief and ultimately the projects are being converted to enable daily testing of the new project system work and the property pages project is VB anyways.

[dsyme]

This is looking great - it will be such a relief to have this done

[dsyme]

@dotnet-bot test Ubuntu16.04 Release_default Build please

[cartermp]

[dsyme]

[brettfo]

@smoothdeveloper What version of Visual Studio and MSBuild do you have installed? As for the 14.0 and 15.0 versions of the Microsoft.VisualStudio.Shell package, both are needed, but duplicate type information should be handled by the PrivateAssets="all" on the first package reference and the aliasing of the 14.0 assembly here.

Also, have you cleaned the repo? There might be some stuff left over in the obj/ directory.

[smoothdeveloper]

@brettfo thanks for the explanations.

I'm using

C:\dev\projects\github.com\microsoft\visualfsharp2>msbuild /version
Microsoft (R) Build Engine version 15.6.82.30579 for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.

15.6.82.30579

(edit: VS2017 Community 15.6.4)

I tried from a clean clone and still having the errors: buildlog.txt

[brettfo]

tl;dr - The evaluation order of targets appears to have changed. I'm looking into it now.

@smoothdeveloper Now I'm seeing the same thing on my box. Doing a quick look it appears that the ResolveReferences target is being invoked by CoreBuild, but that's happening after the Compile target which is what actually invokes csc. In short, Compile is happening before ResolveReferences which seems wrong to me.

Edit: I've created PR #4646 which gets me building on my local box again. We'll see if it passes CI.
Edit 2: CI has passed and I've merged the PR. master should be buildable again on the latest version of VS/MSBuild.