Add factorization to sensor setup

[networxnet]

Might be usefull to add an "factorization" to the sensor setup so that user are able to fill the db with the right value if sensors rawdata has not the right or most common format.

E.g. luftdaten.info's sensor software delivers "Pascal" (Pa) instead of "Hektopascal" (hPa) for air pressure when equiped with BME280. (100758.75 Pa /1007.59 hPa) But hPa is the international common unit for air pressure.

With an factorization setting in openSenseMap's sensor setup you would be able to adjust this units. Useful values would be x0.01/x0.1/x1/x10/x100

[ubergesundheit]

Thanks for your suggestion! There will be a mayor overhaul of the sensor and phenomenon definitions in the future. This feature will definitely considered then