Add affine matrix to phantom mz

[mzaiss]

i dont know if this is planned, but this makes the legacy interpolate and slices compatible with the new affine standard.

two problems:

1. interpolate created some Nans with the new affine reslice. thsi si now caught
2. interpolate must alter the affine, otherwise the phantom size implicitly changes. which is also done here

I also updated the obj size when slices is used, this wasn't done yet also without affine, but should be done.

[SWeinmueller]

Looks fine and everything works for me.
In the future, interpolate and slice function could be depricated and/or _resample_nifit function could be used instead.