getFolderTree  
  abstract fun getFolderTree(selectedFolderId: String, currentFolder: BookmarkFolder?): List<BookmarkFolderItem>
Returns complete list of BookmarkFolderItem inside a folder. This method traverses all folders.
Return
List of BookmarkFolderItem inside a folder
Parameters
selectedFolderId  
the id of the folder.
currentFolder 
folder currently selected, used to determine the current depth in the tree.