weblate 3.5.1

Released on March 10th 2019.

• Fixed Celery systemd unit example.
• Fixed notifications from http repositories with login.
• Fixed race condition in editing source string for monolingual translations.
• Include output of failed addon execution in the logs.
• Improved validation of choices for adding new language.
• Allow to edit file format in component settings.
• Update installation instructions to prefer Python 3.
• Performance and consistency improvements for loading translations.
• Make Microsoft Terminology service compatible with current zeep releases.
• Localization updates.