partial fix for #1257, map download null.zip

pass the title of the map along to geoserver
add doc about this method and the readme field
Change priority of geoserver's package
Updated changelog for version 2.0c5
Remove "or groups" from the upload template until group permissions are supported.  Fixes #1262.
Removed cleardeadlayers command and updated documentation with descriptions for all updatelayers options
Merge branch 'master' of https://github.com/GeoNode/geonode