Implemented goto-tab with Meta+Fn like in Linux text console

Hello,
I have implemented a quick jump to the first 12 terminals using Alt+Fnn keys. This is a feature I am used to, it was missing, now it isn't.
To make it easier to associate a tab with its Fnn key, I changed the default labeling to be 1-based. I find it more useful that way, if a bit less 1337 :P  I did keep it in a separate commit, just in case.
Here's a pull request, if you think this could be useful in your fork as well.
Cheers,
Enrico