Display of lists & enumerables

[richardpawson]

1. For C# & VB, remove the braces added around lists by the Display method. Because they are not used when constructing immutable lists anyway and - unlike in Python- are not presented when you print/return a list in the console.

2. Don't (as at present) render an IEnumerable (iter in Python) as a list. Render it as its type. We need to get the message across early about the difference and the need to cast result to a list for display or to use list methods.

[richardpawson]

Superseded by #191