Ensure tuple field names are handled correctly

[mikedamay]

It is important that we encourage students to use tuple field names rather than Item1, Item2 etc. This may conflict with identifier normalisation. This applies particularly to the exercises tuples and pattern-matching-tuples.

Ensure that tuple field names are handled in accordance with this.

[ErikSchierboom]

It may be that we want to use a combination of a representer and analyzer here. The representer could normalize the names to help reduce the representations whereas the analyzer could comment on using Item1 or Item2.