GUACAMOLE-538: Add System audit permission.

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/permission/SystemPermission.java

@@ -56,6 +56,14 @@ public class SystemPermission implements Permission<SystemPermission.Type> {
          * Create sharing profiles.
          */
         CREATE_SHARING_PROFILE,
+        
+        /**
+         * Audit the system in general, which involves the ability to view
+         * active and historical connection records, user logon records, etc.,
+         * but lacks permission to change any of these details (interact with
+         * active connections, update user accounts, etc).
+         */
+        AUDIT,
 
         /**
          * Administer the system in general, including adding permissions