Set device classes

Set device class for temperature, humidity, pressure and wifi signal strength. Hass will show corresponding icons.

Make update functions async

Fixes warning about blocking I/O functions.

Fix pressure unit of BMx sensors

The unit of atmospheric pressure got corrected from millibar to hectopascal for all BME/BMP sensors.

Add support for BMP and BMP280 sensors

Merge branch 'dev'

# Conflicts:
#	README.md
#	custom_components/local_luftdaten/sensor.py

Updated docs

1.1

Update HACS instructions

First release

Initial release for HACS (Home Assistant Community Store)