tarfile already has the subdirectory structure

Latest release might be for the x230t, not the x230.

x230 is part of the version now

as we want to create release packages per device too

Fixes #142

Closes #133

This is what could go to blobs/x230/ in Heads.

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.