in harvesters and examples normalize DateTime always to UTC

[jmcanterafonseca]

@caa06d9c can this be closed?

[albertoabellagarcia]

not further discussion for 6 months. close it.

[flopezag]

• [ ] weather-forecast (Spain and Portugal )
• [ ] weather-observed (Spain and Portugal)
• [ ] weather stations (Spain)
• [ ] weather stations (Portugal)
• [x] airquality (Madrid)
• [ ] airquality stations (Madrid)
• [ ] airquality (Barcelona)
• [ ] bicycle_hire_station_barcelona
• [ ] import_pois_tourspain