Is it possible to keep Iterator instead of Vec<Vec<String>> in Grid?

[zhiburt]

The idea is,
if we could use Iterator<Item=Iterator<Item=String>> instead of Vec<Vec<String>> we could not allocate a huge chunk of memory.
But we would call the iterator each time we do fmt::Display which would do small allocations each time....
Not sure which is better but...

It potentially could be beneficial, because of less memory usage.

We do use indexes of arrays heavily in papergrid so it may be hard to do.

At the end of the day we would need to benchmark it.

Nevertheless it would affect such things like tabled::Format we would need to store the function until it's applied to iterator or iterator to the element, change it while creating a new iterator.

Not sure if it is valuable and worth to do, but worth to think about it more certainly.

ref: wfxr/csview#27