Update vpd-preload script to support explicit Centaur plugging
Update vpd-preload script to support explicit Centaur plugging

Added a --forceCent parm similar to the --forceProc parm.  It
overrides the default plugging rules for Centaur chips.
I also added a --examples option which prints examples of common
use cases to help people remember.

Change-Id: I933a1897581530b5f89afd1a8ee5a97b2b40d98e
Reviewed-on: http://gfw160.austin.ibm.com:8080/gerrit/3219
Tested-by: Jenkins Server
Reviewed-by: Daniel M. Crowell <912029ca9254ac7b5854e56910561d682e1fa2d0@us.ibm.com>
Reviewed-by: A. Patrick Williams III <c87e37b1a4035affd737b461af89fb722d635f4d@us.ibm.com>

Over-enthusiastic/hostboot,alvintpwang/hostboot,alvintpwang/hostboot,csmart/hostboot,open-power/hostboot,Over-enthusiastic/hostboot,csmart/hostboot,Over-enthusiastic/hostboot,alvintpwang/hostboot,alvintpwang/hostboot,open-power/hostboot,open-power/hostboot,csmart/hostboot,csmart/hostboot,alvintpwang/hostboot,csmart/hostboot,open-power/hostboot,Over-enthusiastic/hostboot,open-power/hostboot,Over-enthusiastic/hostboot