Collection-Names as query prefixes

Names for Collections may be passed independent of the search term as query prefixes.
Ideas:

```
(Umbruch) Wende 
(Umbruch) Umschwung
```

or

```
Umbruch: Wende 
Umbruch: Umschwung
```

or

```
+Umbruch Wende 
+Umbruch Umschwung
```
