Set json file spaces to 4
dialog: integrate progress dialog & confirm dialog to an universal dialog widget
notebook: add confirm dialog on notebook deletion
notebook: remove link,unlink,anchor button
notebook: reset undo history on content loaded
notebook: remove bookmark functionality
filemanager: add grep api
notebook: remove unused asset uploaded by user after every save call
notebook: get title string using grep api to reduce network traffic
filemanager: introduce graceful-fs to avoid EMFILE error