change to working dir for the scripts that use util/.

also, we use the check for x230 in the flashing scripts now. They have
to be run as root now.

Now our scripts start with _where_ it should be run. x230_*.sh should
be run on the x230 where Skulls should be installed. external_*.sh
obviously not.

This also adds the -f <flasher> option and an interactive menu if not
specified.

work in progress #18