Add module level static capabilities

The static capabilities declared in getCapabilities allows certain
capabilities to be queried before instances are created. The intended use
of this capability is to remove the need for the `is_internal_service`
function.

include/maxscale/router.h

@@ -118,6 +118,7 @@ typedef enum router_capability
     RCAP_TYPE_NO_RSESSION   = 0x00010000, /**< Router does not use router sessions */
     RCAP_TYPE_NO_USERS_INIT = 0x00020000, /**< Prevent the loading of authenticator
                                              users when the service is started */
+    RCAP_TYPE_NO_AUTH       = 0x00040000, /**< No `user` or `password` parameter required */
 } mxs_router_capability_t;
 
 typedef enum