Add standart Text Editing key bindings support

[DivineDominion]

As I used nvpy for some serious editing, I noticed neither Opt-Backspace (Mac) nor Ctrl-Backspace (Windows) work to delete a whole word.

Adding some standard keyboard shortcuts would be nice. I'm not sure what people may need; should Alt+Down skip a paragraph, for example? (Emacs style)

Whole-word deletion should be pretty obvious, though.

[mleo2003]

Whole word deletion should be fixed now.