use the valid layer name as file name on the disk
fix the group member add, use join. Fixes #1717
Merge branch 'master' of https://github.com/GeoNode/geonode
remove erroneous MAP_BASELAYERS definition in local_settings.
Merge pull request #1716 from simod/issue-1713

use the valid layer name as file name on the disk, fixes #1713