changed Debian Mirror

Swapped deb_mirror to http://debian.tu-bs.de/debian for faster download
in Germany
editor nano added

added 'nano' to the default install as it is much easier to handle than
vim
editor nano added

added 'nano' to the default install as it is much easier to handle than
vim
changed default keyboard layout to german

changed default keyboard layout to german as of wheezy-build-script