Added ArchivaUser interface to obtain the active principal.
Added ArchivaXworkUser implementation to obtain principal from redback-xwork-integration layer.
Updated (Default)UserRepositories to utilize redback SecuritySystem.isAuthorized() properly.
Updated BrowseAction and ShowArtifactAction to show the limited view provided.
git-svn-id: https://svn.apache.org/repos/asf/maven/archiva/branches@591410 13f79535-47bb-0310-9956-ffa450edef68