[settings] Rename DVDs category to Discs and add an option to specify the handling of Blu-rays.
[FileItem] Also check for MovieObject.bdmv in IsBDFile().
[bluray] Use "disc.playback" setting to start Blu-ray playback.
Treat bluray directories like images and discs when playing them via the context menu.
Merge pull request #5228 from ace20022/blu_select2

[bluray] Add a setting for preferred bd playback