Single precision testing

Recently, antsRegistration is enhanced to be able to process data in single precision. The related changes were pushed to ANTs repository, but there were no test related to them.
The problem was that new tests could not be feeded by double type initial transforms. I converted those double type initial transforms to single precision type using the newly enhanced BRAINSTransformConvert tool.
Then, I added some tests for the antsRegistration in single precision mode. Test changes and related baselines are commited here.