Add warning dialog when deleting non-empty LVM2 PVs (#670171)

When attempting to delete a non-empty LVM2 Physical Volume (one which is
still a member of a Volume Group) display a warning dialog which
includes the VG name and a list of the PV members to allow the user to
make an informed choice whether to go ahead and perform the deletion or
cancel to the operation.  This dialog is displayed when a partition
containing a PV is being deleted or being overwritten by being
reformatted or pasted into.

Bug #670171 - Add LVM PV read-write support