Conform dicomwrappers.Wrapper to the SpatialImage API #797
Description
Following up on #796, the DICOM bits are lagging most of the rest of the code in terms of the APIs that have now been around 2-6 years, such as the .affine propery to .get_fdata().
A useful effort would be to conform this interface to the SpatialImage API and deprecate the old ways of accessing that data.