Python Grainlift toolkit v0.3.1

Published to PyPI as grainlift 0.3.1.

• Bound parameter batches are limited by what one request carries (Limits.request_bytes, or object storage's upload limit), not by Limits.batch_bytes. The native driver sizes bind turns from the advertised request limit alone, so a batch that fit the request but exceeded batch_bytes (1 MiB by default, below the 2 MiB request limit) was rejected with "Bind batch exceeds configured limit".
• A result batch may be as large as anything a client can bind, so a service can return what it accepted. The HTTP response limit follows.
• Verified with the native driver and grainlift's shared conformance suite, including its new request-limit and object storage tests (69 passed).