restructure the GeoNode-GeoExplorer.js file so that it is easier to use an SDK application in GeoNode, a new mixin class was added in a separate file that is mixed in with GeoNode.Composer, an can be mixed in with any gxp.Viewer of an SDK application
Merge pull request #815 from bartvde/sdkappnew

restructure the GeoNode-GeoExplorer.js file so that it is easier to use ...