DiskInformation with serial and flags

Add the device serial number and some flags to the DiskInformation
object. The serial number is available in all devices, volumes and
even core storage devices on a particular device. The device model
is also available.
Serial Linker

Links whole disks by their device serial number. The model and serial
number are both used in the symlinks for more human readability. There
is no straight-forward way to identify physical whole disks, but the
implemented heuristic seems to work well.