ENH: Adding masking of fixed and moving image for registration

Change-Id: I74452c2ce04ff3b2e40ce2ab8534a1ae10124977
Rename the registration tests file to sitkMethodRegistrationTests

Change-Id: I105e40c86538bb27e874d077a200c4e84dda294b
Create itk SpatialObject from image with conversion

Adding code to create the correct itkSpatialObject from the provided
image, by doing an image cast. It should be possible to create a
spatial object that takes an arbitrary image, including a label map
image, and uses if for the mask.

Change-Id: I05d7567a1c79c3089cad243eca25ee749d118a0b
Move the logic for checking the dimensions of mask match

The internal create spatial object method now assumes that the
dimensions match prior to the call this allows for better converge
and error messages.

Change-Id: I6efbdf80d4352174fe894ddc586b63abb475ab4e
Adding testing of mask with registration

Change-Id: I4be6408bf1d25b67896e6b05c4d8553c3de63c00
Merge topic 'SIMPLEITK-558_RegistrationAddFixedMovingMasks' into next

602eea1d Adding testing of mask with registration
ca8b5abf Move the logic for checking the dimensions of mask match
e95b4629 Create itk SpatialObject from image with conversion
ac48d4f1 Rename the registration tests file to sitkMethodRegistrationTests
b8e3f786 ENH: Adding masking of fixed and moving image for registration