Properly store post locations

[moonfloof]

Currently, the location of a post is simply just a string. It would be nice if actual locations could be stored separately and include more details about them within posts, so check-ins would be better supported. This would mean adding another field to the main posts table to check for a location ID.

EDIT: Perhaps the location field could simply be a JSON-encoded string containing all fields related to location on the IndieWeb wiki.