youtube-dl: myvideo, rtmp support

Hello,

i have rewrite the MyVideoIE from an XBMC plugin. I hope the license is ok.
  Original Code from: https://github.com/dersphere/plugin.video.myvideo_de.git (scraper.py)
  Copyright (C) 2013 Tristan Fischer (sphere@dersphere.de) - GPLv3/GPLv2 ?

This is a fix for https://github.com/rg3/youtube-dl/issues/247

my test enviroment:
  Python 3.3.1
  RTMPDump v2.4 (last git, with DEBUG flag)

successful tested videos:
  http://www.myvideo.de/watch/8229274/bowling_fail_or_win 
  http://www.myvideo.de/watch/8418541/Deichkind_Leider_geil 
  http://www.myvideo.de/watch/8328930/Nickelback_When_We_Stand_Together_Official_Video 
  http://www.myvideo.de/watch/8357965/Maria_Mena_Homeless 
  http://www.myvideo.de/watch/9049079/Kosheen_Catch 
  http://www.myvideo.de/watch/9104080/Avril_Lavigne_Here_s_To_Never_Growing_Up