Switch to PostgreSQL

[RCgmbh]

Instead of text/json files, store all data within PostgreSQL. Use PostGIS to store and query all geo data. This will allow to quickly find close data, such as pictures, POIs, past nearby positions etc.

The goal here is to do some basic work (db connection, general thoughts), and additional issues will need to be created to implement the specific DataConnectors. The existing file based connectors will be kept to allow for low-profile backup clients. So maybe we will build this against common interfaces for file- and pg- based data storage.