Fix/async influxdb connector#21

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19201080 wants to merge 3 commits intomainfrom

fix/async_influxdb_connector

Commits on Dec 11, 2020

Replace influxdb with influxdb-client in the requirements
19201080
committed
Remove methods ensure_database and delete from DatabaseConnector
19201080
committed
Adapt DatabaseConnector to influxdb-client library and switch to async write method
19201080
committed