Add accessor method to get the optimizer scales.

If this ivar is explicitly set by the user, than that values is always
returned. If it is estimated, then that values is only available while
the registration is running.

Change-Id: If07936d2a5b4de72240db27797fa04632feac40b
Adding doxygen documentation for the GetOptimizerScales method

Change-Id: I021b05af02c9d442f8060fd54fde5c451789c341
Adding example which utilizes center estimator and scales estimator

This example also exercises, the new GetOptimizerScales.

Change-Id: I818a0b70c7f55748f4202b17eeef2a1e74cc85ea
Adding baseline images and testing for the registration3 example

Change-Id: Ibf6a8a492da044b9534227bd5b684ac744addead
Merge topic 'SIMPLEITK-575_AddAccessorToOptimizerScales' into next

f45a8e38 Adding baseline images and testing for the registration3 example
51f39ce3 Adding example which utilizes center estimator and scales estimator
c4fd3726 Adding doxygen documentation for the GetOptimizerScales method
ccef92bd Add accessor method to get the optimizer scales.