MSMUtils and login fixes

* Review this class to allow its use for external authorizations
* Fix on Manager viewport for internal auth
* Use internal auth as default in manager login

Now you can enable the external authorization with this configuration in `managerConfig.js`:

```
    {
        "ptype": "mxp_login",
        "pluginId": "loginTool",
        "externalHeaders": true,
        "actionTarget":{
          "target": "north.tbar",
          "index": 3
        }
    }
```

Then the login plugin will check the user information and never override the `Authorization` header that must be initiliazed in an external system (for example Apache httpd)