Support for local files

[Elinvention]

I think MumbleDJ should support local files too. We could define a folder in the configuration file that limits accessible files and allows MumbleDJ to scan that folder to look for audio files. Then users will be able to run a commands like !listlocalsongs, and !add file.ogg.

[matthieugrieger]

This is something that has been requested from other users, I hope to implement this soon!