Repository Title accessor: Made separator configurable by reference formatter.

The separator between Referencenumber and Title, depends on the current reference number formatter. Therefore i implement the seperator configurable by the `ReferenceNumberFormatter`. 

`dotted`:
![bildschirmfoto 2013-11-14 um 20 17 24](https://f.cloud.github.com/assets/485755/1544057/6929291a-4d61-11e3-924f-5cf54bce8709.png)

`grouped_by_three`:
![bildschirmfoto 2013-11-14 um 20 15 16](https://f.cloud.github.com/assets/485755/1544045/4d5a5754-4d61-11e3-83cc-1d357c807fda.png)