pbs: fix vague 'Full Episode' titles; prepend name of show

pbs: fix vague 'Full Episode' titles; prepend name of show

Many videos are given the title 'Full Episode' or 'Episode x', etc;
in the info json 'title' is the episode title (for oneshots this is
'Full Episode') while the program name is 'program':{'title'. This
changes the title from '(episode title)' to
 '(program name) - (episode title)'

The following urls demonstrate useless titles

    http://video.pbs.org/video/2365367186/
    http://video.pbs.org/video/2365519307/
    http://video.pbs.org/video/2365527039/
    http://video.pbs.org/video/2365530605/

Before change

    Full Episode
    Episode 5 | Preview
    Season 3 | Episode 4 Preview
    July 17, 2015

After change

    To Catch A Comet - Full Episode
    The Crimson Field - Episode 5 | Preview
    Last Tango in Halifax - Season 3 | Episode 4 Preview
    Charlie Rose The Week - July 17, 2015