Show Backreferences on file_view.

@maethu We now show backreferences in file view.

![bildschirmfoto 2014-02-27 um 11 38 52](https://f.cloud.github.com/assets/358342/2283011/2a80ae6a-9fb7-11e3-9fef-87455a7dc987.png)
![bildschirmfoto 2014-02-27 um 11 38 45](https://f.cloud.github.com/assets/358342/2283012/2a8117e2-9fb7-11e3-91e8-de2f7174a791.png)
![bildschirmfoto 2014-02-27 um 14 34 33](https://f.cloud.github.com/assets/358342/2283010/2a801aa4-9fb7-11e3-852a-cf97c0adbe04.png)

Note If we have circular references we only show that it references the other file not that it gets referenced by it.