MBR: add partition table UUID and partition UUID

[thirdeyenick]

This allows to retrieve the partition table UUID and partition UUID for MBR formatted disks. The partition table UUID (aka "disk identifier" or "disk signature") can be used to identify a disk when using the MBR format scheme. The partition UUID is then just the partition table UUID with the partitions index number appended.

[deitch]

I was surprised that mbr.initTable() was unused, but apparently it was.

The UUID is optional in MBR, but it cannot hurt, so might as well.

Thank you for this.

[deitch]

Some linting errors.

[thirdeyenick]

Some linting errors.

Should be fixed now.