Plex API support for IMDB

[SwiftPanda16]

@dane22 Just a reminder that includeGuids=1 was implemented for this exact reason.

[implemented] Add includeGuids URL parameter to return external Guids

External metadata guids were implemented for the new Plex Movie and Plex TV Series agent in this previous feature request. Example: <Guid id="imdb://tt5433138"/> <Guid id="tmdb://385128"/> <Guid id="tvdb://8856"/> However, these external guids are only available when retrieving the metadata XML for a single item (i.e. /library/metadata/<ratingKey>). They are not available when retrieving the contents of a library (i.e. /library/sections/<librarySectionID>/all). Many 3rd party applications d…