Switching to JointHistogram MI metric

When using Mattes MI the optimizer sometime has very large step sizes
when very close the the optimal position. The yields unstable results,
due to stepping out side of the overlapping regions.

Change-Id: I15b95a833d40090b901e48801bd984f17a2434dc
Adding verification of for python ImageRegistrationMethod2

Also the example has been update to match the CXX example.

relax tolerances some too

Change-Id: Ia258a854aaaa9a91499c3b61cbfb4a7b029989ab
Adding baseline image for demons registration examples

Also made the number of iteration match the cxx example

Change-Id: I70d8a6976fc0de996b5fb75cbd6af052f8d7c29f
Always print dart measurement for RMSDifference

This will enable better tracking of the value when the test fails, by
allowing graphing of both the passing and failures in the cdash web
interface.

Change-Id: I3d028368e8351bcc97c7ec77810ec01dc752a62c
Merge topic 'SIMPLEITK-536_CreateTransformTestingInfrastructure' into next

868a203a Always print dart measurement for RMSDifference
9e15701d Adding baseline image for demons registration examples
2f258187 Adding verification of for python ImageRegistrationMethod2
7ffae01d Switching to JointHistogram MI metric