Add German Weather Service (DWD) as new weather ION
This Commit adds a new ion for the weather dataengine. Uses the Deutschen Wetterdienst (DWD) as data source. Has seven day forecast, warnings and, if available, current measurements.
For getting the available stations it downloads a file containing all the stations, parses and filters it. The parsing is quite basic. In every line it jumps to the relevant bytes. If the ever change the format of the file, this could break the whole search. Perhaps it would be better to implement a more sophisticated parsing? Also the file contains a lot of station, some of them do not work with the APIs I use. I decided to radically remove a lot of stations and only keep some. This should remove all non working stations, but also removes a lot of station which are working. The stations that remain seem to always have a forecast and current measurements. I couldn't find a way to quickly determine if a station is working or not. The question is: do we want to supply less stations with all (probably) working or do we want to return more stations, but some not working at all?