Add support for F# as a language type

This came in as a feature request from [uservoice](https://feedback.azure.com/forums/327234-azure-data-lake/suggestions/10608288-native-support-for-f-with-usql), opening this issue to track discussion and refine the suggestion. This is the text from uservoice

> It would be great to see some F# support for USQL. I understand that you can already do UDFs in any .NET language (provided you inherit from the required base class or interface etc.) but having F# inline with USQL would be excellent. F#'s lightweight syntax and expression-based syntax would be a natural fit with the SQL section of USQL, and I think would provide a more seamless experience switching when between SQL and .NET code than SQL and C#.
>
> Pushing this further one could envisage an F# / USQL type provider along the lines of the SQL Client one (http://fsprojects.github.io/FSharp.Data.SqlClient/) which could allow you to consume USQL from within F# directly.