Signals list that DownloadManager, ProcessWrapper 
threads send (DownloadThread.py)

HANDLER
=======

SignalHandler.py

  class DownloadHandler()
    def handle(self, msg):
      .
      .
      .

HEADER
======

[
'finish',	Download thread finished
'close',	Download thread stopped by the user
'error',	Error occured while downloading
'playlist',	Playlist current download no/from
'youtube',	Pre-Processing
'download',	Download stuff [size, percent, eta, speed]
'ffmpeg',	Post-Processing
'ignore',	Ignore this header
'remove',	Removing extra DASH files
'filename',	Extract DASH extra filenames
]

      
INDEX
=====

index == -1:	GLOBAL
index != -1:	URL IN COLUMN

DATA
====

e.g.
['57.3%', '20.63MiB', '542.44KiB/s', '00:16']

DATA-PACK
=========

DataPack.header = header
DataPack.index = index
DataPack.data = data