This adds parts for:
1. iterating over the segments
2. using an interface for writing the segments
3. stubs for handling deleted segments
Change-Id: I76a17cac6deb0b6c042a8ab7c4155a890db9da84
Implements creating roughly load-balanced set of batched
that can be used to make multiple requests.
Change-Id: I349b276176dcb8ba9163e7e06a94509d73fa5ddc