Kernel RPMs now auto-install to boot partition

[Daniel Drake]

Hi,

Found some time to implement something that has been desired for a
while: now when you install a kernel RPM on the XO, it will
additionally auto-install to the boot partition, so now you can just
install a new kernel RPM with rpm/yum and reboot and expect it to be
used, no additional steps needed.

The root of this strange behaviour (installing kernels twice) is due
to the design of the update system, there might be room to improve on
this in future as well, but at least this detail will now be less
annoying to developers.

Daniel