Remove unused Partition(path) constructor

History:

1) The constructor was added by commit:

    6d8b169e
    2006-03-14 21:37:47
    changed the way devices and partitions store their devicepaths.  Instead of

2) Removed from most of the file system specific ::Copy() methods by
   commit:

    ad9f2126
    2006-03-19 15:30:20
    fixed issues with copying (see also #335004) cleanups + added FIXME added

3) Removed from GParted_Core::copy() method by commit:

    7bb7e8a8
    2006-05-23 22:17:34
    Use ped_device_read and ped_device_write instead of 'dd' to copy

4) Finally removed from the last place in xfs::Copy() method by commit:

    e414b71b
    2012-01-11 19:49:13
    Update xfs resize and copy to use new helper functions

The Partition(path) constructor is no longer used.  Remove.