Make default site Language configurable and fix site translation

[JohnMwashuma]

User story

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Ensure that Arabic Language is in place throughout the system and Arabic language is the default one for particular deployments.

Acceptance Criteria

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• [x] Default site language should be configurable per deployment.
• [x] One should be able to translate a page based on the language selected.

Task check list

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• [x] Make LANGUAGE_CODE Django settings configurable and pass appropriate value on ansible inventories group var's.
• [x] Update locale function to the following:

  def locale(request):
  locale = request.session.get('locale') or getattr(
      settings, "LANGUAGE_CODE", None)
  if locale and translation.check_for_language(locale):
      translation.activate(locale)
  return {"locale": locale}

• [x] Make sure all magic strings are wrapped in translation.
• [x] Remake locale messages using python manage.py makemessages -l ar
• [x] Translate the msgid property inside the django.po file where the msgstr is msgstr "" to Arabic and recompile the messages using python manage.py compilemessages
• [x] Make datatables language definitions dynamic based on the current locale/language code.

[faith-mutua]

@JohnMwashuma the login page loads with Arabic set as the default language. A user is able to translate the pages without any problem.