sortOn: sorts range of aggregates by member name(s)

["Nordlöw" via Digitalmars-d]

On Wednesday, 5 November 2014 at 14:36:11 UTC, Marc Schütz wrote:
> It's intuitive and concise. Plus, Ruby uses `sort` and 
> `sort_by` for the same functionality, exactly in parallel, so 
> it will be familiar to many users.

Here's my first working but primitive version.

https://github.com/nordlow/justd/blob/master/sort_ex.d#L15

How do I extend it to support

- variadic number of extractors
- sortBy("x")

?