Add switch to override LubeLogger fills with Fuelio fills

[tigattack]

The script has a function, find_duplicate_fillups, which is currently only used as a mechanism to warn the user when a fillup is found in LubeLogger with the same date and mileage as a fillup in Fuelio, but is otherwise unmatched (e.g. different notes or switches).

As a new feature, I'd like to add a switch allowing Fuelio to be enforced as the 'source of truth', i.e. if a fillup in Lubelogger appears to be a partial duplicate (based on the logic described above), it is patched or replaced with the fillup from Fuelio.

Pending hargata/lubelog#541.