ENH: move CastImageToITK to ProcessObject class

Change location to parrent of method so that it can be utilized by the
ImageRegistrationMethod class.

Change-Id: I11de8672064c4ead15d0487347ff9445ac872a62
ENH: Adding initial ImageRegistrationMethod

Adding basic method with just the MeanSquares Metric and the
RegularStepGradientDescent optimizer. This is created in a new
registration directory.

Change-Id: I6cc7f85119f3e1e169b61c550206c6af55afcd19
Starting basic C++ testing for ImageRegistrationMethod

Change-Id: I47db63a69df51e75fe21010f45c310bb7c15a253
Adding basic ImageRegistrationMethod python example

Based on ITK's v3 ImageRegistraion1 Example. This example show how to
do this with SimpleITK.

Change-Id: I41489161d11dc61a9c59cc62357d8ecc3118f60e
Adding ImageRegistrationMethod1 example for C++

Change-Id: Ie04f1769d8c71929e3817c5deaa712303e66ce54
Merge topic 'SIMPLEITK-521_AddInitialRegistrationComponents' into next

7caa4bb7 Adding ImageRegistrationMethod1 example for C++
78e93c62 Adding basic ImageRegistrationMethod python example
1e5e7dad Starting basic C++ testing for ImageRegistrationMethod
df31f6b9 ENH: Adding initial ImageRegistrationMethod
d6517da2 ENH: move CastImageToITK to ProcessObject class