AllUsersAndInboxesVocabulary: In a one client setup the client Title should not be added to the item 

When delegating a task the items in the Responsible field are prefixed with the client title. In a one-client setup this information makes no sense. 
![bildschirmfoto 2013-07-29 um 08 42 38](https://f.cloud.github.com/assets/485755/869951/5e27bbcc-f81a-11e2-8ae7-dedfe69a85df.png)


Therefore the vocabulary should be improved, so that the items are only prefixed with the client title in a multiclient setup.

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