Support parallel/portfolio testing in .NET Core builds

[pdeligia]

Using .NET Core, PSharpTester currently works only in sequential mode (no portfolio or parallel testing). The reason is that WCF (which we are currently using to spawn and control multiple testing processes in parallel) is not fully supported in .NET Core (and it will not be).

We will investigate using ASP.NET Core instead to achieve the same functionality.

[alexreinking]

What WCF-specific functionality does P# rely on? Can it be replaced with System.IO.Pipelines in .NET Core? There's also an official WCF client under development in .NET Core. So maybe the tester could be easily ported to be entirely .NET Core?