Interactive Scripting Improvements Tracking Issue

[iwillspeak]

Our current REPL leaves a little to be desired. It would be nice if we had a better embeddable scripting API in the compiler so state could be carried across from one evaluation to the next.

• Multi-statement support in the REPL.
• Dotnet interactive support.
• #!r and #!nuget
• -e, --exec immediate script mode
• -s, --script script execute mode
• Syntax highlighting in the REPL