Merge remote-tracking branch 'upstream/develop' into feature/theming2

* upstream/develop:
  Fix color fallback order
  Use console.warn instead of console.log
  Get rid of mutation_types file, use inline approach. Minor fixes
  Add fallback color rule.
  Change english validation error messages
  Clean up the code
  Validate name presence on client-side as well
  Better styling for client-side validation. Add I18n for validation errors.
  Fix broken ToS link. Fix linter errors
  Add client validation for registration form
  Use Array.reduce instead of lodash.reduce
  Humanize validation errors returned on registration
  Added user option to hide instance-specific panel, rearranged config screen to better categorize it / adjustments to language selector
  fix