Create an API layer for external process (eg: FsAutoComplete)

Description

Today, there is no more integration with ionide F# plugin (through FsAutoComplete).
With the current implementation (FSAC directly referencing FSharpLint.Core), it means both FSharpLint & FSAC must share the same version of FSharp.Compiler.Service.

As discussed in https://github.com/fsharp/FsAutoComplete/issues/942, an alternative solution could be to implement a API layer between FSharpLint.Core & FSAC, so FSharp.Compiler.Service could be abstracted using dedicated types (same solution that Fantomas is using)

To summarize the integration with FSAC this new API :

sequenceDiagram
    box green FsAutoComplete process
    participant FsAutoComplete
    participant FSharpLint.Client
    end
    box blue FSharpLint process
    participant FSharpLint.Console
    end
    FsAutoComplete->>FSharpLint.Client: GetDaemon
    FSharpLint.Client->>FSharpLint.Console: Start Daemon
    FSharpLint.Console-->>FSharpLint.Client: 
    FSharpLint.Client->FSharpLint.Console: Setup jsonrpc
    FSharpLint.Console-->>FSharpLint.Client: 
    FSharpLint.Client-->>FsAutoComplete: 
    Note over FsAutoComplete,FSharpLint.Client: Later, when a lint is needed
    FsAutoComplete->>FSharpLint.Client: LintRequest
    FSharpLint.Client->>FSharpLint.Console: LintRequest
    FSharpLint.Console->>FSharpLint.Console: Lint with FSharp.Compiler.Service
    FSharpLint.Console-->>FSharpLint.Client: LintResponse<br/>(no FSharp.Compiler.Service types here)
    FSharpLint.Client-->>FsAutoComplete: LintResponse

TODO:

• Create the lib layer (Add FSharpLint.Client project) (#637)
• Expose a version method for the Client/Console flow (#637)
• Setup the build process to release FSharpLint.Client as a new nuget (#637)
• Expose a lint method (that will call val lintFile : optionalParams:OptionalLintParameters -> filePath:string -> LintResult method) (#663)

I would like a confirmation that this feature is ok for you guys and I'm willing to work on it

Start by reviewing the proposed FSharpLint.Client layer and the existing FSharpLint.Core Application/Lint.fsi lintFile entry point. The work is complete when the Client project exposes version and lint methods, can communicate with the Console without FSharp.Compiler.Service types, and is included in the build and released as a NuGet package.