.NET Core 1.0 RTM support and upgrade to Json.NET 9

[gmarz]

• NET45 and NET46 targets are built with msbuild

• NETStandard1.3 target is built with the dotnet cli (preview2)

• Bump Json.Net to 9.0.1

• Removed auxiliary projects from Elasticsearch.Dotnet.sln (.NET core
  solution)

• project.json files now only list .NET core frameworks

• Include gitlink symbol files in nuget packages

• Various build script fixes and refactoring

  Unrelated change:

• Renamed code generation projects:

  • CodeGeneration.LowLevelClient => ApiGenerator
  • Nest.Litterateur => DocGenerator

NOTE: We now rely on nuget pack and explicit nuspec files. Dependencies between the nuspec file and project.json files can diverge -- we should add validation to the script to ensure they stay in sync until the dotnet tooling becomes official (and we can dotnet all the things). Will open a separate PR for this.

Closes #2138

/cc many thanks to @phenixdotnet for getting this going :)

[phenixdotnet]

You're welcome :)

One question: Why doesn't include the .NET 4.6 and other in the project.json and keep only on build system ? dotnet cli is now RTM and can produce full .NET dll/exe. It will much simplier to maintain no ?

[Mpdreamz]

@phenixdotnet the core libraries are RTM but the tooling is still in preview. We rely heavily on NCrunch as part of our daily dev and that won't move over until the dotnet tooling are also RTM. I'm also still waiting on solid version manager support for the dotnet tooling to feel confident switching fully.

Our 2.x build is DNX all the way which atleast had a go live license (and a version manager :)), once the dotnet tooling is RTM and NCrunch supports it we'll move over fully too.

@gmarz our 2.x core support is targetting dotnet5.1 which should be equivalent to netstandard 1.0. Why the bump to netstandard 1.3? This will limit the number of platforms we support.

[russcam]

I can't get the tests running in this branch. Need to dig into it deeper, but looks like a compatibility issue with TFMs for test project and dotnet tooling

Project 'C:\Users\russ\source\elasticsearch-net-master\src\Tests\project.json' does not support framework: DNX,Version=v4.5.1.
Project 'C:\Users\russ\source\elasticsearch-net-master\src\Tests\project.json' does not support framework: DNXCore,Version=v5.0.
SUMMARY: Total: 2 targets, Passed: 0, Failed: 2.
Running build failed.
Error:
System.Exception: Failed to run dotnet tooling for dotnet.exe args: ["test"; ""C:\Users\russ\source\elasticsearch-net-master\src\Tests""]
at FSI_0005.Paths.Tooling.DotNetTooling.ExecWithTimeout[a,b,c](a runtime, b failedF, c workingDirectory, IEnumerable1 arguments, TimeSpan timeout) at FSI_0005.Testing.Tests.Test@74.Invoke(String project) at Microsoft.FSharp.Collections.SeqModule.Iterate[T](FSharpFunc2 action, IEnumerable1 source) at FSI_0005.Testing.Tests.RunUnitTests@82.Invoke(String project) at Microsoft.FSharp.Collections.SeqModule.Iterate[T](FSharpFunc2 action, IEnumerable1 source) at FSI_0005.Targets.clo@38-22.Invoke(Unit _arg4) at Fake.TargetHelper.runSingleTarget(TargetTemplate1 target) in C:\code\fake\src\app\FakeLib\TargetHelper.fs:line 492