Default configuration is now translated in-place

Drupal 8's configuration translation system was so far based on the assumption that configuration shipped with modules is imported as-is, and that imported configuration is translatable from its English source with configuration translation. While that is perfect in concept, it was a huge usability problem in actual site use because people were unable to edit their maintenance mode settings, menus or views in their original version due to the translations overriding text values. They would need to edit their translations for text but their original configuration for functionality (eg. adding more fields in views). Configuration created later on a monolingual site was created in the foreign language of the site and therefore behave differently.

To restore the expected user behavior and still support translating shipped configuration we now do the following:

1. When installing locale module (such as installing Drupal in a foreign language), all active configuration that came with projects as default configuration is switched to the site's default language.
2. Parts of that configuration that still conform to the original default configuration structure is translated in-place.
3. Support for translating this configuration is still included with localization updates and interface transltion's user interface.