Issue #2516914 by eojthebrave: Enabling this module removes non-Amazon Upload destination options in field settings.

- Do not limit user's ability to set URI scheme for file fields during
  initial field configuration, but, once they've chosen a widget, do limit
  the URI scheme to just Amazon S3 where appropriate.

[#2178823] sagannotcarl - Fix possible duplicate upload if file is not removed from copy of the form AJAX uses to rebuild the form.

[#2162033] s201 - Use protocol relative URLs for making AJAX requests. Allows module to work in both http and https modes.

- Adds an #s3_acl property to the amazons3_cors element.
- Adds widget settings for each field that allows a user to select
  what ACL permissions to use for files uploaded via the file
  field.

- Use Drupal.settings.basePath when constructing the URL for signing
  a CORS upload.

- This caused the CORS 'key' field to get set to /myfile.jpg when it should have
  been myfile.jpg and files would get uploaded in to a directory with no name in
  S3.

The widget provided by this module only works with the s3 uri scheme no sense in displaying others.