rbac: merge module's cans from and into existing roles

example: add permissions into existing 'developer.local' role
```js
    api.rbac(ret.data = { supromongod:{ cfg:{ rbac: mongo_rbac()}}})

    function mongo_rbac(){
        return {
            roles: {
                'developer.local':[
                    'module.supromongod',//it has '*' but anyway
                    '/supromongod/lib/',// it has '*' but anyway
                    'App.supromongod.view.ControlTools',
                ]
            }
        }
    }
```

Signed-off-by: Oleg Verych <olecom@gmail.com>