Error Estimation

I translated the example Using F# Quotations for Error Estimation from Chapter 9 of Expert F# (Introducing Language-Oriented Programming) to Scala. I don't use anything as fancy as F# quotations. Instead, I simply create a new arithmetic type for estimates, and use implicit views to handily convert from the usual arithmetic types.

The example also translates nicely into Haskell by using the numeric type classes.