Arvados

I was looking for a function that iterated all items from an Arvados API list. The function that does this is arvados.util.keyset_list_all but I overlooked it because the name didn't sound like a match:

1. I don't understand what "keyset" is here.
2. "list" makes it sound like it builds and returns a list rather than an iterator.

It would be best if this function was named iter_all_by_X, if we can come up with an X that's more descriptive than "keyset".

Failing that, even iter_all would be a better name, although admittedly it's a valuable one too that we'd rather reserve.

We can rename the function in the definition and then retain API compatibility by just adding keyset_list_all = iter_all_new_name to arvados.util.