deprecations.

Missing how to retrieve and store the Galería token from libsecret.

Add the possibility of export to Shotwell. This works with Shotwell in a clean
state; in theory it should work with a full Shotwell, but I haven't tested it.

You can copy only GPS, or exclude GPS and/or date and time.

By default, interpolate-gps only interpolates a range of photos where the
extemes have GPS data, and are close in space (1000 meters) and time (1 day).
This option allows to force an interpolation even with far away photographs.