Match Gray Basemap cache levels to other ESRI basemaps

ChrisKahn

Currently, the gray canvas basemap only goes to the 1:9000 zoom level.  Most other basemaps go to 1:1128 (esri streets, topo, Bing, OSM, etc).  It's annoying to users to switch from all the other basemaps and not have Gray be available in a web application.