requested to merge issue/yaml_content-3086366:3086366-content-import-ui into 8.x-1.x
- Added a form for importing YAML Content files which is accessible from a "YAML Content" tab on the main content listing page in the admin UI. This form allows users to import YAML content files from a module, profile, or a directory which they can specify. Users can also import from a Zip archive which they can upload. In all cases there is an option to select individual files for import instead of importing all the available files.
- This MR includes only new functionality for adding a user interface. No pre-existing YAML Content logic was changed.