Add/edit more metadata for audio files

[bengodden]

As the database grows it might nice to be able to organize the transcribed files by fields of their id3 tags. (i.e. Filter to show all files from a particular speaker, region, time period, etc if someone is trying to get used to a particular voice, dialect, speed or speech pattern).

Also the ability to delete files (suggestion to limit this to some type of admin privileged).

[aaronfay]

@bengodden do you have a list of attributes that we might want to start with? This is pretty open-ended, unless the feature request is to just allow for tags.