WavePlus_Bridge

New feature: Add timestamp to the MQTT publishing.

Bug fix: A reopening of a big CSV databases may have led to a corruption of it due to an incorrect placement of the file write pointer.

Switch for the example MQTT broker from mqtt.eclipseprojects.io to test.mosquitto.org due to better response time.

Fix of issue https://github.com/Drolla/WavePlus_Bridge/issues/8 (Application crashes if 'period' or'data_retention' are not explicitly defined by the YAML file).

Update README.md