Added /stadfang endpoint

[sse87]

New endpoint, here is an old issue about it: #242

Just like /calendar it's not a scraper but it has all the data in stadfang.js which exports an array of strings. 118907 items to be exact.

Example of a string:
103836;Ármúli 42;108;Ármúli;Ármúla;42;;64.13349537;-21.87428225
It's split into:
landNumber;address;zipCode;streetNf;streetThf;houseNumber;houseLetter;latitude;longitude

Like described in the docs at least one of the filter parameters must be provided:
address, zipCode, street, number, letter, landNumber or coordinates (latitude and longitude)

Only optional is radius which is only used when coordinates are provided and default value is '1.0'

Checklist

• Write tests
• Write documentation