Delete audio files when they are removed/replaced

[hahn-kev]

Describe the feature
Right now if I replace existing audio, or I remove the audio all together, all that does is remove the reference to a media file. The media file is left in place. We would like to also delete that media file. The main reason is that this matches FLEx, because it does not allow multiple references to the same media file it will delete them when the one reference to them is removed. Until FLEx matches how this works we should also delete media files when they are removed.