Batch writes fail with lots of items

The batchWrite mechanism should chunk out the seed arrays into blocks and invoke each of these with a batch call.

Start by locating the JavaScript implementation of the batchWrite mechanism and how it receives seed arrays. Verify the current behavior with a large seed array, then ensure the arrays are split into blocks and each block is sent through a batch call; done means large batch writes complete successfully.

Written by the indexing model from the issue text.