see #125

this should be stuff used by any supported type of hardware and helps #93
or #102

thanks for the link in #103

see #100

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

put some emphasis on choosing an image and support flashing any 4M image
externally.

This may help in refurbishing an x230 laptop.

the update function already uses it

upgrade.sh is gone

All we do is the bios vendor/version check. We can do that in any case.
Requirements don't change.

This patch adds two new payloads (memtestx86 and coreinfo)
to resolve #74.

thanks @alex-kazda

Fixes #85