added test for distortion correction
fix in accessors

- removed redundant variable in applyDeform
- added NOFORM for orientation in mrimage to indicate when no
  orientation has been set
- ints not longer accepted to interpolation functions, to prevent
  confusion when casting to base class
allow 3d image to motioncorr, working convertDeform
fully functional  distortion correction!, added another test for
distortion correction (not run automatically though)