Notify changes on files on upload behavior

Currently, changes to the files property of nuxeo-upload-behavior won't trigger change notification events, which prevents double binding from working properly.

For example, doing something like this will fail to propagate changes to myFiles:

<nuxeo-file value="{{document.properties.myprop}}" files="{{myFiles}}"></nuxeo-file>

Use case
populate the title field with the name of the file uploaded:
[customer name]
I had a custom create layout within a search drawer and when a user uploaded a claim they wanted the title field to fill with the name of the screenshot and have that be the default value