rarbgapi: add support for searching by show/movie ID
rarbgapi: add support for searching by show/movie ID

E.g. to search a TV show using the TheTVDB ID the `search_tvdb` argument
can be passed to the `search` function.
Supported are: `search_imdb`, `search_tvdb` and `search_themoviedb`

verybada/rarbgapi