This time, only some code optimization, reducing the number of lines of python code with about 20%.
- Adding a MeasuringSensor class which is used for all measuring sensors, to shorten the python code (won't affect users)
- Adding device_class Illuminance to illuminance sensors (will change the icon to default Home Asssistant icon)
- Using default unit of measurements from Home Assistant constants (won't affect users)
Changes were based on a small part of the changes as proposed in beta 0.7.1 by @Magalex2x14, further developed by me (@Ernst79).