Update vi bindings

The following normal mode bindings are added:
    o, I, A, gg, G, g^, g$, x, X, backspace, d*, D, s, S, c*, C, ~, gu,
    gU, J, K, y*, Y, p, P

I was not able to add binding for 'O'

dd now deletes the whole line as vim, while D deletes the line to the
end. c, s, y act the same way