[GEOS-6789] Add support for Advertised and Transient parameter in GWC

This pull request contains a fix for JIRA: https://jira.codehaus.org/browse/GEOS-6789.

For the GWC side you may refer to https://github.com/GeoWebCache/geowebcache/issues/292.

This pull request requires that the pull request https://github.com/GeoWebCache/geowebcache/pull/293 in GWC has already been merged.