Secure replication method
Curently, unsecured metacat replication action is easy to break the replication
setup. But it couldn't create a new replication without adding certification to
metacat java lib.
Actions in MetacatReplication class, such as "start", "stop" and "servercontrol"
et al, need be secured. We may use the approach in "buildindex" action in
MetaCatServelet class, it only allow administrator can operate this action.