Make sure the sign in button is shown to intranet anonymous users

In some GeoMapFish projects, anonymous users connecting with an IP address from the intranet are assigned an "intranet" role (with a faked "intranet" user object). This PR makes sure the "login" buttons are then still available so that those users may still sign in with an actual username/password. As for now they only get a "logout" button.

Here is a brief summary of what users will see in the top toolbar:
* internet anonymous users: "login" button
* intranet anonymous users: "Logged in as ..." + "login" button
* internet loggedin users:  "Logged in as ..." + "Account" button ("logout" + "change password")
* intranet loggedin users:  "Logged in as ..." + "Account" button ("logout" + "change password")