GUI: externalize cmdline?

[equalsraf]

Opening this because @khalidchawtany pinged me earlier but I really have no idea what to do with the externalized cmdline yet :)

[teto]

having a cmdline popup in the middle of the window would be cool. I dsilike the CLI cmdline at the bottom because I have to look down on it instead of looking at the text. I would vote for something like sublimetext palette.

[jgehrig]

Closing this issue. The work can be tracked via Pull #586.