Removing Kernel menu.
Add kernel restart button to toolbar.
Cleaning up output management in code and menus.
Removing unneeded select prev/next from Edit menu.
Adding back Kernel menu and Cell Type submenu.
Converting loops in *_all_output to $.map().
Simplified Cell menu items related to output.
Adding DOM ids for each menu.
Merge pull request #4662 from ellisonbg/menu-cleanup

Menu cleanup