Add a test entry for sagittal mosaic images

[joshuacwnewton]

SCT recently released a 'Sagittal mosaic' QC report, which is similar to the existing axial mosaics, except each sub-image is much larger. Meaning, often times the generated image will exceed the viewport by a significant amount. I'm not sure how the current implementation will handle this, so it might be nice to add a test image. :)

Such a report can be generated using this SCT test, but just to make things easier, here's a zipped up copy generated locally: qc.zip

(The current jQuery-based QC handles this pretty poorly, so the bar is not high here. 😅)