Re: jsonb_delete with arrays

> Attached is an implantation of jsonb_delete that instead of taking a
single key to remove accepts an array of keys

Since I already saw this patch, here is my small review.

Speaking about implementation of `jsonb_delete_array` - it's fine, but I
would like to suggest two modifications:

* create a separate helper function for jsonb delete operation, to use it
in both `jsonb_delete` and `jsonb_delete_array`. It will help to
concentrate related logic in one place.

* use variadic arguments for `jsonb_delete_array`. For rare cases, when
someone decides to use this function directly instead of corresponding
operator. It will be more consistent with `jsonb_delete` from my point of
view, because it's transition from `jsonb_delete(data, 'key')` to
`jsonb_delete(data, 'key1', 'key2')` is more smooth, than to
`jsonb_delete(data, '{key1, key2}')`.

I've attached a patch with these modifications. What do you think?