[Bug] Setup script fails to set BigQuery IAM permissions

[troyraen]

The script setup_broker.sh contains the following lines, which fail because this command only works for tables, not datasets:

bq add-iam-policy-binding \
    --member="allUsers" \
    --role="roles/bigquery.metadataViewer" \
    "${bq_dataset}"
bq add-iam-policy-binding \
    --member="allUsers" \
    --role="roles/bigquery.dataViewer" \
    "${bq_dataset}"

For proper instructions, see Grant access to a dataset.

This change should be included with #147