Add back FSI printing of R values

[AndrewIOM]

Proposed Changes

The old distribution method had an .fsx file that called in the pretty printer for R into interactive scripts. I have moved this into the RProvider itself and deleted the old RProvider.fsx file that is now redundant.

Note: the solution here doesn't actually work! Need to find a solution for this when using a #r "nuget:RProvider" reference.

Addresses #241

Types of changes

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• [x] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

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• [x] Build and tests pass locally
• [ ] I have added tests that prove my fix is effective or that my feature works (if appropriate)
• [x] I have added necessary documentation (if appropriate)

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[kMutagene]

This might not be a satisfactory fix, but in all projects where i provide fsi printers i just add an FSIPrinters module and add instructions to the docs on how to register those via fsi.AddPrinter.

As the function used here is very easy, it still would help to just add a note on the docs about using fsi.AddPrinter(fun (synexpr:RDotNet.SymbolicExpression) -> synexpr.Print())