* FEATURE: Default Composer Category Site Setting
- Create the default_composer_category site setting
- Replace general_category_id logic for auto selecting the composer
category
- Prevent Uncategorized from being selected if not allowed
- Add default_composer_category option to seeded categories
- Create a migration to populate the default_composer_category site
setting if there is a general_category_id populated
- Added some tests
* Add missing translation for the new site setting
* fix some js tests
* Just check that the header value is null