[META] File management (media browser, fields on files etc)

We may want to consider expanding the functionality supported by core for file entities. Particularly, it would be good to provide the same functionality as the File Entity contrib module for drupal: https://www.drupal.org/project/file_entity

Things that would be good to have:

• [ ] #1380 Upload multiple files at once
• Reusing files via media browser
  • [ ] #2718 Create another interface (view) for listing manage uploaded files for internal system use named "Media Library Selector" or similar. Its goal is to provide a way to list files and allow the user to select one for use by the calling form element/mechanism.
  • [ ] #2720 Create a new form which wraps two of the above items together:
    • Upload new file
    • Choose an item from the Media Library Selector view
  • [ ] #1307 Create a new file field widget that implements the above new form so that the user can easily upload a new managed file, or select an existing one.
  • [ ] #2719 Modify the CKEditor image dialog to use the new form when adding a new image to the content
• [ ] #2721 Create a new dynamic file field formatter that attempts to handle output of any file appropriately for its file/mime type.
• [ ] #4007 alt + title fields

Things that are done:

• [x] Files that are proper entities
• [x] #2375 An interface to list and manage uploaded files
• [x] #2796 Add the ability to edit an existing managed file
• [x] #2633 A way to upload a file outside of file fields or Rich-Text editor uploads
• [x] #2632 Core fieldable file entity bundles
  • [x] Determine core file entity bundles (image, document, other?)
  • [x] Make bundles fieldable

Related Issues around garbage collection:

• [ ] #2896 Side-wide settings for garbage collection
• [ ] #2897 File entity garbage collection settings
• [ ] #2898 Admin interface for manual garbage collection
• [ ] #2899 Confirmation dialog for orphaned files