TST: Improved tests for DcmMetaExtension.from_sequence
BF+TST: Fix from_sequence and _get_change_class in DcmMetaExtension
TST: Add tests for NiftiWrapper.__init__
BF+TST: Fixes for slices_valid and samples_valid methods of NiftiWrapper.
BF+TST: Fix get_meta and checks for valid meta classes
RF: Got rid of generate_splits method.

Split method is now a generator.
BF+TST: Fixes and tests for NiftiWrapper.split

Fixes issue where the time dimension was getting lost when splitting on it.
TST: Added tests for NiftiWrapper.from_dicom
ENH+TST: Improved handling of affines.

Set both sform and qform in nifti header, and set the affine attribute in the Nifti1Image instance.
BF+TST: Update translation in any affines when splitting on slice dim
ENH: NiftiWrapper.from_dicom handles DPS to NPS transform

Instead oh handling it in DicomStack.get_affine.
BF+TST: Fix scaling issue when joining slices.
BF: Don't set slope_intercept in from_sequence
ENH: Allow nibabel to set the nifti transforms in default manner.

Don't try to store the affine in the qform. This is more consistent with nibabel and avoids issues with loss of precision in the qform.
BF+TST: Improved preservation of Nifti header info that is consistent in from_sequence.
BF+TST: Fixes and tests for from_sequence
ENH: Added some default exclude regexes.

Eliminate more potential sources of PHI.
BF: Make the value for dummies the max for int16 dtype

We currently always output the nifti in int16 dtype since some tools (i.e. fslview) do not like unsigned int types.
TST: Updated tests to reflect changes from previous commit.
TST+BF: Handle merging datasets without unspecified slice dimension.