Flexible OnLoginListener

Allow more actions with carried simpleFacebook. For example:

```java
new OnLoginListener() {
    @Override
    public void onLogin(SimpleFacebook simpleFacebook) {
        simpleFacebook.getProfile(new OnProfileListener() {
            @Override
            public void onComplete(Profile profile) {
                // saveProfile(profile);
            }
        });
    }
};
```