videodatabasedirectory: replace all the CDirectoryNode implementations that provide a list of grouped items with CDirectoryNodeGrouped
musicdb: support filtering in GetYearsNav()
musicdb: add GetItems() to retrieve a list of items of a specific type and GetItemById()
musicdatabasedirectory: replace all the CDirectoryNode implementations that provide a list of grouped items with CDirectoryNodeGrouped
CSmartPlaylistDirectory: add support for grouping to music smartplaylists
smartplaylists: add mixed grouping support
CSmartPlaylistDirectory: integrate mixed grouping
CGUIDialogSmartPlaylistEditor: integrate group options
CGUIWindowVideoBase: implement forced enabling/disabling of grouping into movie sets
[confluence] add controls for grouping in SmartPlaylistEditor.xml