Better wording when task has finished
Revamp the alert styling
For the task completion message, use 'success' style
Add rounded corners for lightbox popup
Alerts: fixed flickering on Chromium

The fade in effect is already handled by jQuery and there's no need to
interfere with it by applying extra styles.
Delete handle_language and handle_project from PootleCommand workflow
Move does_not_exist function
Create TranslationProject.disable_if_missing method
Merge update_stores and update_translation_projects commands