Support playback of local files

- Recursive listing of available files
- Protected against path traversal attacks
- Does not follow symlinks
- Possibility to ignore directories or files with specific names
- If no exact match for the requested track can be found, the bot plays
the track with the best match
- If multiple tracks match the user gets a message listing all
candidates

configuration.ini

@@ -4,6 +4,8 @@ volume = 0.1
 admin = BafTac
 music_folder = /home/fabian/music/mumblebot/
 tmp_folder = /tmp/
+ignored_folders = tmp
+ignored_files = Thumbs.db
 is_proxified = True
 
 [debug]
@@ -35,6 +37,7 @@ not_playing = Aucun stream en lecture
 bad_file = Bad file asked
 no_file = Not file here
 bad_url = Bad URL asked
+multiple_matches = Track not found! Possible candidates:
 
 help = Command available:
        <br />!play_file <path>