Add cities geocoding resolver

• imports cities from GeoNames TXT files in a local index file.
• allows full text search queries using whoosh Python library
• adds a new endpoint to return the results based on a search query

/geocoding?q=Geneva:

Limitations

• Searching for random cities hangs or takes very long

To improve

• Move the endpoint to /api?
• Decide were to store the various files, cities and index
• Better file path handling to correctly resolve paths to files from the root