Prepare documents and mails for separate styling when they're removed 

* Extend body class for removed documents or mails, this allow us to display specific icons and wartermarks for removed objects.
* Prefix links of removed documents with an additional removed span. This allow us to display and additional icon in front of the regular icon for all removed documents in the trash listing. (An global implementation, which would work for all document_listings is not necessary, because all removed document has to be trashed before.)

Examples:

![bildschirmfoto 2014-11-27 um 08 14 29](https://cloud.githubusercontent.com/assets/485755/5213471/50068c1c-760e-11e4-977b-a1e913779a5d.png)
![bildschirmfoto 2014-11-27 um 08 18 15](https://cloud.githubusercontent.com/assets/485755/5213472/50073892-760e-11e4-9d58-a2510695a092.png)

Styling Issue will follow separately on package `plonetheme.teamraum`. 

@lukasgraf please have a look ...
I personally would prefer `' '.join((body_class, 'removed'))` here.