TEMP workaround for #9813
Image marshal includes zoomLevelScaling
viewport.js $ viewportImage.js pass zoomLevelScaling down to PanoJS
PanoJS handles zoomLevelScaling - default is still 50%
Use zoom scaling levels from server
Blitz img.getZoomLevelScaling() returns 2**n scaling
Merge pull request #979 from will-moore/big_images_FS_9701_dev44

Big images fs 9701 dev44