Add the ability to download a youtube playlist.

The dapl and dvpl commands take playlist URL or ID as paramters and
download all the audio or video tracks in the playlist respectively. It
creates a subdirectory in the default download directory named the same
as the playlist name. It then downloads all the tracks into the
subdirectory.
Update changes
Remove repeated code (#110)

Replace invalid characters in subdirectory name
Merge branch 'pr/110' into develop
Merge branch 'develop' into autodetect-terminal-size
Enable da and dv command for playlist results
Updated changes
Add the ability to download all the playlists by a user.

The daupl and dvupl commands allow the user to download the audio or the
video for all the tracks in all the playlists for a user respectively.
Merge pull request #114 from mtahmed/mtahmed-develop

Add the ability to download all the playlists by a user.
tidy help text
add --no-preload option
Merge branch 'develop' into autodetect-terminal-size

Conflicts:
	mps_youtube/main.py