Add a menu to set default tabs and shell arrangement

It would be great to have a menu to set up several tabs with different things (shells, commands, interpreters) for default. I'm running a script via Guake Hooks start which do the job I want:

```bash
#!/usr/bin/env bash
guake &
sleep 1 &&
guake --new-tab=1 --execute-command=ipython &&
guake --tab-index=1 --rename-tab="Ipython" &&
guake --new-tab=2 --execute-command=htop &&
guake --tab-index=2 --rename-tab="Htop" &&
guake --select-tab=0
```

but I think it would be a nice feature for Guake to have it via a menu in preferences .