L2SS-1582: Add statistics aggregator

.coveragerc

.gitlab-ci.yml

README.md

infra/jobs/central/aggregate.levant.nomad

lofar_stingray/_logging.py

lofar_stingray/_minio.py

lofar_stingray/aggregate.py

lofar_stingray/aggregator/__init__.py

lofar_stingray/aggregator/_base.py

lofar_stingray/aggregator/_bst_aggregator.py

lofar_stingray/aggregator/_sst_aggregator.py

lofar_stingray/aggregator/_xst_aggregator.py

lofar_stingray/reader/__init__.py

lofar_stingray/reader/_s3_packet_loader.py

lofar_stingray/record.py

requirements.txt

setup.cfg

tests/aggregator/__init__.py

tests/aggregator/bst.json

tests/aggregator/metadata.json