Remove last trace of cylinder size adjustments in the resize dialog (#749867)

This commit from 2010-05-20 removed use of cylinder size increase in the
minimum, and cylinder size decrease in the maximum file system sizes
from the resize/move dialog.
    e62a23b5
    Add partition alignment option to align to MiB (#617409)

This cylinder size limit adjustments were being performed using the
Dialog_Base_Partition::BUF member variable.  Now in the
Dialog_Partition_Resize_Move class it is never accessed, and only
unnecessarily set.  Move BUF from the common base class into the
Dialog_Partition_Copy class where it is still used.

Bug 749867 - Some limits are adjusted by arcane cylinder size amount
             when copying and resizing in a single operation