MetaImage Reader/Writer should respect `Origin` tag

[jpsacha]

The MetaImage tag Origin (same as Position and Offset tags) specifies real-world coordinates of the (0,0,0) index in an image, see ITK MetaIO documentation. it should be mapped to ImagePlus Calibration's: xOrigin, yOrigin, and zOrigin.

[jpsacha]

ImageJ origin is expressed in pixels (not in real-world units like mm).