Add option to toggle visibilty to customize which space it's on

[MilesConn]

I was really happy to see toggle-visibility implemented and it's one of my favorite features of iterm2. A nice thing to have would be to be able to customize which space (virtual desktop) it's on. The current behaviour is the terminal opens where it was last hidden. iterm has a very complicated approach to this that I've never been able to get right.

The main thing I want is the ability to toggle-visbility on my current space with just one screen, thinking using a laptop and having editor and browser in different places. However, there are other settings that people might want like

1. always toggle current space and current screen
2. where cursor is
3. main screen, main space

I have a lot of free time right now as I'm inbetween jobs so I'm happy to try and take a stab at this.