Switch to the tessdata-fast Tesseract model, instead of the tessdata
one. The tessdata-fast Tesseract model is much smaller, and a bit faster
than the other one. Also, it's the model that Debian/Fedora ship by
default.
Closes#545
Remove the Kurdish (Arabic) language ("kur_ara") from the list of
languages that we offer for OCR, since it's not included in the
installed languages.
Interestingly, it is not present in the Apline Linux repos as well, so
this was probably an omission in the first place.
Restore the OCR languages to the state they were in
66d3c40163, with some minor changes. We
can now do so because we download all the trained models, not just the
ones that Alpine Linux offers.