STYLE: Make 12 public TransformBase member functions private
STYLE: Make 12 public TransformBase member functions private

It appears that the member functions that are made `private` with this commit are never directly called outside the class implementation.

Private members are easier to maintain than public members.

SuperElastix/elastix,SuperElastix/elastix,SuperElastix/elastix,SuperElastix/elastix,SuperElastix/elastix