Feature/movie support

[danrahn]

Movie Support

With the introduction of credits markers, there's a much stronger justification for adding movie support to this editor. This PR does just that. In the UI, movie libraries are now selectable in the dropdown and search results act the ~same as an episode row - the name of the movie and number of existing markers, and clicking on the row shows/hides the marker table, and adding/editing a marker will show thumbnails (if enabled). Movies are also integrated into the purge detection system to allow recovery of markers that Plex wipes out after analysis. Moves are not integrated into bulk actions, and likely won't unless there's a more compelling reason to.

Key technical changes:

• Generalize the idea of a "base" media item - an item that can have markers attached directly to it, i.e. an episode or movie. Adjust things throughout by changing e.g. episode_id to parent_id, episode to baseItem, etc.
• Similar to above, generalize the idea of a "top-level" media item - an item that is the root type for a section, i.e. a show or movie.
• Also similar to above, add intermediate base classes for many structures that were previously specific to episodes/shows (e.g. PurgeTable becomes the base class for MoviePurgeTable and TVPurgeTable, with most of the logic remaining in PurgeTable).
  • Note that the lack of multiple inheritance makes the above points somewhat awkward. It would be great to have generic "base item" interfaces that movies and episodes implement and "top-level" interfaces that movies and shows implement, but a class can only inherit from one base class, which occasionally results in the movie version of an item inheriting from a common show or episode class, but duplicating code for the type that it doesn't inherit from.
• Deal with different "levels" of section maps. Everything assumed that we have a Section > Show > Season > Episode > Marker hierarchy, but with movies it's just Section > Movie > Markers. Handle this somewhat ungracefully by switching on the library type whenever we're processing a section or "top-level" item (a movie or show).
• Add a new ResultRow class for movies, which is extremely similar to EpisodeResultRow.
• Allow marker tables to be lazy-initialized. With episodes, it's usually reasonably fast to iterate over all items in a season and get existing markers (and determine if the underlying file exists if using ffmpeg for thumbnails), but we could potentially have thousands of movies in our search results, and that could be incredibly slow if we need to check the underlying files for each one.
• Unrelated to movies/credits: Vastly improve startup performance of building our marker cache. Instead of creating a query that combines markers and media items, grab both separately and combine manually, resulting in a ~10x improvement on my own library.