Navigation Hotkeys

Adds new key combinations for easier notebook navigation.

Edit-mode hotkeys:

• pageup - scroll page up
• pagedown - scroll page down
• Alt- + - Split cell and keep cursor position
• Alt- - - Combine cell and keep cursor position
• Alt-n - Toggle line number display in current codecell
• Shift-Enter - Execute cell, goto next cell and stay in edit mode if next cell is a code cell or unredered markdown cell
• Ctrl-Enter - Execute cell and stay in edit mode if cell is a code cell
• Ctrl-y - toggle celltype between markdown and code

Command-mode hotkeys:

• esc - toggle to edit mode
• home - Go to top of notebook
• end - Go to bottom of notebook
• pageup - scroll page up
• pagedown - scroll page down