ENH: Add PowellOptimizerv4 to ITKv4 registration

Powell optimizer is converted from the ITKv3 to v4 registration
framework. A test is designed for this newly converted optimizer
and is passed successfully.

Change-Id: I136ba2851f76b7c0b920c620c166d93173b93201
Merge topic 'PowellOptv4'

41f1e51e ENH: Add PowellOptimizerv4 to ITKv4 registration