CFileItem: add IsLibraryFolder()
video: fix "Set content" showing for library folders (genres etc.)
CFileItem: extend GetVideoContentType() to detect movie sets
CVideoDatabase: refactor SetDetail() into SetSingleValue()
fix
DatabaseUtils: add GetField() and MediaTypeFromVideoContentType()
CVideoDatabase: add SetSingleValue() overloads
media: move "Edit title" context menu entry under new "Manage ..." entry