TEMP workaround for #9813
Image marshal includes zoomLevelScaling
viewport.js $ viewportImage.js pass zoomLevelScaling down to PanoJS
PanoJS handles zoomLevelScaling - default is still 50%
Add PyramidService.getResolutionDescriptions method (See #9813)

Provide a list of ResolutionDescription objects which should
eventually represent the entire geometry of the tiled plane.
Use zoom scaling levels from server
Merge pull request #634 from will-moore/big_images_FS_9701

Big images fs 9701 (develop)