nixos/geoclue2: make configurable, can whitelist applications

All options within geoclue.conf[0] have been made configurable.

Additonally, we can now specify whether or not GeoClue
should ask the agent to authorize an application like so:
```
services.geoclue2.appConfig."redshift" = {
  isAllowed = true;
  isSystem = true;
};
```

[0]: https://gitlab.freedesktop.org/geoclue/geoclue/blob/2.5.2/data/geoclue.conf.in



Co-authored-by: worldofpeace <worldofpeace@protonmail.ch>