ENH: Restore/convert/repair ImageRegistrationHistogramPlotter

ImageRegistrationHistogramPlotter was never converted to the new
statistics framework. This patch restores, converts and repairs the
example.

Also, added a regression test.

Change-Id: I7f86e454b34bffbb36bc4a7023973a8c0c346db8
Merge topic 'ImageRegistrationHistogramPlotter'

cfd4341 ENH: Restore/convert/repair ImageRegistrationHistogramPlotter