Update directory.json

add giessen
add kassel
Merge pull request #29 from benny-de/patch-1

Update directory.json, kassel and giessen
comma settings
added Fuerth; updated Franken
Merge pull request #30 from mojoaxel/master

added Fürth
Merge pull request #28 from freifunk-ffm/generator-refactoring

Generator refactoring