Tidy up POI definition, and also YAML structure
Tidy up POI definition, and also YAML structure

- A POI may have mutiple categories.
- POI can also have tags
- The URL is pointing to an external website for the POI
- Currently there is no fields what_makes_it_sweet (pretty much the poi.description) and location_title (poi name itself) in POI.
OpenCityProject/ocp-docker,OpenCityProject/ocp-docker,OpenCityProject/ocp-docker