Added importer community module.

The importer modules were previously exclusively part of the OpenGeo Suite.
updating module names to include Importer prefix
updating sources to include copyright headers
Removing dependency on restlet json, using net.sf.json instead
removing hard dependencies on libs inheireted on geoserver main
removing preview link to geoexplorer
Merge branch 'master' into importer

Conflicts:
	src/community/pom.xml
	src/web/app/pom.xml
Merge pull request #285 from jdeolive/importer

Added importer community module.
Merge branch 'master' of git://github.com/geoserver/geoserver