Merge pull request #4282 from Montellese/movie_set_fixes

Fix "Manage movie sets..." doing nothing when there are no sets available
[settings] move audio stream language from locale to video settings
[settings] better grouping under Video|Music->Library settings
[settings] pause after refresh should be a child of enable refresh rate, and sync type is a child of sync to display
[settings] arrange/enable PVR settings a little nicer
[settings] replaygain and crossfading subsettings should enable based on the state of their parent
[settings] audio rip settings are children of the encoder type
[settings] upnp announcements depend on the upnp server being enabled
[settings] the video screen settings are children of the monitor setting
[settings] enable/disable audio setting controls based on state rather than hiding them
[settings] masterlock at start is a child setting of masterlock being enabled
[settings] move subtitle downloading to the bottom of the subtitles section
[settings] move preferred subtitle language below languages to download
[settings] move subtitle stereoscopic depth next to subtitle position on screen
[settings] cleanup video decoding settings (hw-accel + frame-multi-threaded) by moving them to their own settings category
[subtitles] change settings logic for subtitle storage location (make it a spinner)
[settings] enable teletext scaling only if teletext is enabled
[settings] pvrpowermanagement settings/timers to be dependent on powermanagement being enabled
[subtitles] drop 'prefer external' option, always preferring
[settings] drop unused videolibrary.seasonthumbs