Add option to disable the prefix opening chat with prefix prefilled

[leijurv]

I am referring to how when you type . it opens chat and prefills .. This is exactly like the vanilla mechanic with /.

Two reasons:

1. On Dvorak, the key . is typed with the physical qwerty key e, which is open inventory. I can't open my inventory with the prefix as ..
2. I cannot bind anything to that key. In ClickGUI when I try and change a keybind and type that same key, it just opens chat instead of setting the bind.

I'm fine with hitting T then . like a normal human.

[leijurv]

Added in 4.7

[leijurv]

You're welcome, other dvorak users

(yes i know i'm just talking to myself)