Better support for login/logout on multilingual sites

Hi, 

When testing multilingual sites we have to override many out-of-the-box keywords. For example the log out command checks:

```
Page should contain     Logged out
```

We should think about better methods to check such common pages or actions or provide some css classes/ids in source to allow to check on. For my tests i use a keyword-file for each language i want to test on, maybe we can provide a nice boilerplate in p.a.robotframework for such needs. This fix refs to #11.