This class contains the key information that describes a nrrd file
The expectation is that it will be generated by parsing an existing file
before loading. It will also be generated before saving a file.
It should be handed off to NrrdFile reader/writer in order to save/load
It is conceptually similar to ImageJ's FileInfo class, but I have decided
not to derive it from that because I would like to make this package
detachable from ImageJ.