Mostly PBS Kids rewrite

- Removed os.getcwd
- The cove api interface to PBS kids was missing some shows
- Changed to json api used on website
- Using show list from there instead of pbs.org list, quicker
- Video playback logic now, attempts to use ipad link
- If that fails it tries rtmp, checking for both flv/mp4
- Most episodes have SAMI type subtitles, XBMC supports needs but need
cleaning first