L2SS-359: Add grafana, prometheus, and a tango->prometheus bridge.

docker-compose/grafana.yml

docker-compose/grafana/Dockerfile

docker-compose/grafana/dashboards/lofar2.0-station.json

docker-compose/grafana/data_sources/aa

docker-compose/grafana/data_sources/ab

docker-compose/prometheus.yml

docker-compose/prometheus/Dockerfile

docker-compose/prometheus/prometheus.yml

docker-compose/tango-prometheus-exporter.yml

docker-compose/tango-prometheus-exporter/Dockerfile

docker-compose/tango-prometheus-exporter/LICENSE

docker-compose/tango-prometheus-exporter/Makefile

docker-compose/tango-prometheus-exporter/code/collector.py

...mpose/tango-prometheus-exporter/code/pip-requirements.txt

docker-compose/tango-prometheus-exporter/get_metrics.sh