Fix for downloading subtitles for http videos

Should fix problems reported here:
- http://forum.xbmc.org/showthread.php?tid=188250&pid=1645765#pid1645765
- http://forum.xbmc.org/showthread.php?pid=1646161#pid1646161

Also improved logging a bit to make spotting issues a little easier and removed the gui setting to configure the custom subtitle path.