Create run_kernel context manager
Simplify ExecutePreprocessor using new context manager

Closes gh-6447
Copy file metadata in atomic save

Closes gh-6405
Preserve symlinks in atomic writing
Added on_bulk_change method in WidgetModel
optimization of WidgetModel.apply_update
Adding a comment and renaming on_bulk_change to on_change
Don't rewrap markdown input in markdown output
Add scrollmanager
Make slideshow toolbar add classes to modified cells.
Fixed bug
Added smooth scroll to replace std browser behavior.
Add ScrollManager to global ipy namespace in main.js instead of,
in the bottom of the scroll manager js file.
Added scroll mode selector,
fixed rebase conflicts.
Added heading and slideshow scroll managers
Fixed rebase indents
Removed ScrollManager selector combo.
Address review comments
options bug fix
Added comments clarifying scroll units