Add a boot to login screen option to raspi-config

[KenT2]

Just been playing with raspi-config and updating the wiki page for wheezy raspbian, The boot selection approach is really good now.

It would be nice if the boot_method menu had a third option - to boot to the login screen. I can see situations where having an open login is not good in households with more than one Pi user.

Teenager to Dad, was it you that broke my lovely xyz app with your clumsy attempts to get into the modern world!