Separates the MedicalViewerCells based on the DICOM Information.
For each DICOM dataset, the loader passes the information to the DicomInstanceCellSeparator class, and returns the cell where the image will be displayed. This allows the logic for separating the cells to be based on any criteria. When the DicomInstanceCellSeparator class needs a new cell to be created to display an image, it will request the cell from a factory (passed via the constructor). Then it saves the cell with separation information (i.e. patient position, orientation). When another DICOM Instance is passed it can use the same cell to display that instance (stack of images). This class will separate based on the image position.