Added support to use the new 'Trailers' plugin to handle trailers functionality. Main advantage is that you can get more than one trailer back from online or even locally.
Changed the default trailer site util to 'YouTube'.
Improved trailers handling esp. for tv episode specials (use episode name in youtube searches when season == 0).

Also removed some overloaded methods which were not used internally (and hopefully not externally). Marked them Internal as they are not really something that should be accessed externally from the trakt plugin.