Update the Nuxeo File Widget so that users can remove a selected file

When using the File Widget in the Edit window the user cannot remove the selected file.

Current State:
1. User enters Edit view.
2. User selects a file.
3. User clicks cancel.
4. User enters Edit view and file is still listed. User can select a new file, but cannot remove the old file.

To remove the old file reference completely the user has to leave single document view and return to it.

Desired State:
1. User enters Edit View
2. User selects a file.
3. User can remove the selected file, make additional metadata updates and Save the changes.

See the attached video for the current behavior.
See the attached png for an arrow pointing to where a mouse-over action could be added to allow for removal of the file or just adding a remove icon would be useful.