Add local workspace remove prefix configuration

Currently by default the capabilities document produced from virtual workspaces will remove the namespace prefix from the layer names.  This commit adds a configuraton option to disable this behaviour.  This is also a fix for http://jira.codehaus.org/browse/GEOS-5476
Merge pull request #230 from jesseeichar/localWorkspacePrefixConfig-master

Add local workspace remove prefix configuration
Merge branch 'master' of git://github.com/geoserver/geoserver