#766 Show title when switching tabs

[Ernst de Haan]

It would be very nice if iTerm would add an option to show the number and title of a tab when a tab is switched. This applies *especially* to Full Screen mode.

Here's my use-case:
- I use iTerm on a daily basis, mostly in full-screen mode;
- I label every tab properly, each has it's own function (build, edit code, edit tests, etc.)
- I typically remain in full-screen mode all the time except when I get confused about which tab I'm currently in, then I switch to non-full-screen mode temporarily to check out how may tabs I have and which one I'm in now.

I would expect the label to show up in the center of the screen, with a rather large font, showing for just 1 or 2 seconds or so and then fading away quickly.

As a nice-to-have you could keep the label visible as long as the Cmd-key is pressed.

The setting in the iTerm preferences pane could be given three possible values: (1) off, (2) on and (3) only in full screen mode. For me the third option would be my preference, but if I would just have the first two options available, I'd go for option (2).