nuxeo-file widget -- can't delete Blob from document

Clients may have a use case for the nuxeo-file widget in an edit layout. In an example of this, it is possible to change a file attached to a document, but it is not possible to delete a file attached to a document.

Example:

• use attached nuxeo-file-edit-layout – note that nuxeo-file is bound to content field
• Create a new File document with a main blob attachment
• Edit the File document – the widget prompts for Upload (button) or deletion of existing blob (X icon) – click the X icon and save
• the original blob remains attached to the document