Added edl/comskip support over HTSP.

The possibility to skip commercials when streaming a recording over htsp (e.g. from XBMC) has been missing, but now that XBMC (Gotham) supports it, I've added the necessary htsp API changes. It supports two formats of commercial skip data: Comskip and EDL, in that priority order. The code first checks for the presence of a comskip file, and if that isn't found it looks for an edl file. I've tested this first on a modified 3.2 clone, and now on master. 
To use it with XBMC the addon needs to implement the GetRecordingEdl method. I've forked the opdenkapm/xbmc.pvr-addons addon repo to https://github.com/kendrak24/xbmc-pvr-addons (branch hts.pvr_edl) and implemented it there.
This is the first github thing I've done, so I hope everything is correct. Let me know if there is something I need to change...