Added default script references for .NET Core

[ncave]

A quick hack to make script parsing work.

[dsyme]

@ncave I'm OK with this as a temporary thing, but perhaps you could submit an issue and alignment PR to Microsoft/visualfsharp too? Ultimately that's the repo where the Microsoft-supported .NET Core packages for F# will be published from.

Where possible we should include @KevinRansom in this toodiscussion, since we need to be on a path to convergence in the specification of the .NET Core F# scripting programming model.

[dsyme]

@ncave Also, is there any specific reason why you chose this list of types? Is it the set needed to support FSharp.Core?

[ncave]

@dsyme It's an ad-hoc set of dependencies used to pass most of the script tests in the test suite.
I'll open an issue in Microsoft/visualfsharp to possibly get a better solution by @KevinRansom.

[dsyme]

Thanks, please link the issue here

FWIW I think we should also be referencing these assemblies (e.g. System.IO) in .NET Framework F# Interactive scripting. There have been cases that I've had to reference System.IO manually when referencing PCL or .NET Standard components from F# Interactive. It would be better if we just auto-referenced all the relevant .NET Framework facade assemblies that cover the new-style PCL/.NETStandard surface area for "mscorlib", "System" and "System.Core"

[ncave]

Added an issue in Microsoft/visualfsharp: #1272