Report either partition or device in operational results (#743181)

In the operational results of the calibrate step include the type of the
path GParted is working with, either partition or whole disk device.  Do
the same for the create empty partition step too for consistency, even
though it only ever creates partitions.  Looks like:

    create empty partition
      path: /dev/sdb3 (partition)
      start: 2099200
      end: 4196351
      size: 2097152 (1.00 GiB)

    calibrate /dev/sdc
      path: /dev/sdc (device)
      start: 0
      end: 1953525167
      size: 1953525168 (931.51 GiB)

Makes it explicit to the users what GParted has detected.  Helps the
developers when looking at saved results to understand what decisions
were made and why specific steps were performed or not.

Bug 743181 - Add unpartitioned drive read-write support