Docker installation - missing language files

[rgraf]

By docker deployment may happen that some language files are missing. In particular "django.mo". This results in some missing important menu items, such as "Information package creation". To fix this either is required to follow documentation here: https://github.com/E-ARK-Software/earkweb/blob/master/docs/install_manual.md or copy these files to related location before "docker-compose build" (e.g. earkweb/locale/en/LC_MESSAGES for english language).