Support user_configuration

Merge all workers (but tesseract_fr_best) into one and add these parameters:

• lang, replace current CLI argument (and update worker_configuration docker.command), enum, choices (fra, nld, spa, lat, nep, ara)

Do not add any parameters to tesseract_fr_best. You can set in the configuration the following:

lang: fra
model_dir: /usr/share/teklia/models