v7

A minor release, including the following changes:

• Switch the notification templates to working with v3 schema introduced in the previous release. Before that they would produce nonsense when describing revisions.
• Implement kcidb_load_queue - a Google Cloud Function optimizing the submission loading to avoid exceeding BigQuery load job quota and stalling. Pull submissions from the queue explicitly, providing more information on the speed of processing and the outstanding data, than the previously-used Google Cloud Function retry system would. Explicit pulling also allows holding submissions in the queue while upgrading or debugging without losing data. The new implementation could still hit the quota, but the probability of that is low, and so is complexity. Rename the previous implementation to kcidb_load_message.
• Optimize I/O data merging to speed up 3+ dataset cases dramatically. This is particularly useful for bundling submissions before loading to BigQuery in kcidb_load_queue.
• Add kcidb-count tool outputting the total number of objects (revisions/builds/tests) contained in I/O data. The underlying implementation is used to calculate cut-off point when collecting submissions to load in kcidb_load_queue.