[emms-help] Stream playlist support

[Lucas Bonnet]

Hello everybody !

EMMS now supports stream playlists, ie URLs like : 

http://www.somafm.com/tagstrance.pls

I added a special type for that, called playlist.

A variable has changed, `emms-stream-default-action', be sure to change
it. It should be "add" or "play", and no longer 'emms-add-url or
'emms-play-url.

Code is more or less tested, if you experiment bugs, be sure to
complain.

-- 
Lucas