Rework awm key bindings

- Remove an overridden default binding

  I didn't realize I was overriding it, so I clearly don't use it

- Add mail binding

  Shuffled around other bindings a bit to free up modkey + m

- Change up some bindings

  Mainly to move them over to the right side of the keyboard. This makes
  them easier to hit (though probably less intuitive).

- Use variable names for program bindings
Bind zsh accept-line to ctrl-i

I use `accept-line` frequently in combination with `expand-or-complete`,
which is ctrl-i, so having it bound to ctrl-o makes it more convenient
to type. This overrides the default `accept-line-and-down-history`,
which I don't use.