* Changed sensor attributes for GPS
the sensor is now using the correct attributes (latitued and
longitued) which enables them to show up on the map.
* added option to display the sensor on the map
the configuration will be extended by the optional 'show_on_map' flag.
Default is not display the sensor on the map.
* making the change non-breaking: old default behaviour
* removed doubled attributes for lat and lon
* Add sensor platform for luftdaten.info
* Add monitored conditions to platform schema
* Make monitored conditions config obligatory
* Improve inline documentation
* Import first standard libs then 3rd party libs
* Combine resource url using format
* Remove unnecessary try..except block
* Use state “None” instead of STATE_UNKNOWN
* Minor changes incl. removal of unused vars
* Add missing spaces